Q.1 What is the normal resting heart rate range for an adult?
50–60 beats per minute
60–100 beats per minute
100–120 beats per minute
120–150 beats per minute
Explanation - A resting heart rate between 60 and 100 bpm is considered normal for adults; rates below 60 may indicate bradycardia, while rates above 100 suggest tachycardia.
Correct answer is: 60–100 beats per minute
Q.2 Which electrode placement is used for Lead I in a standard 12‑lead ECG?
Right arm to left arm
Right arm to left leg
Left arm to left leg
Right arm to left arm and right arm to left leg simultaneously
Explanation - Lead I measures the potential difference between the right and left arms, giving a horizontal view of the heart's electrical activity.
Correct answer is: Right arm to left arm
Q.3 What is the primary purpose of the high‑pass filter in ECG instrumentation?
Remove baseline wander
Attenuate muscle noise
Suppress high‑frequency interference
Increase signal amplitude
Explanation - A high‑pass filter eliminates low‑frequency baseline drift caused by breathing or electrode motion, preserving the morphology of the QRS complex.
Correct answer is: Remove baseline wander
Q.4 Which artifact is most likely caused by movement of the leads during exercise?
Power line interference
Baseline drift
Muscle artifact
Motion artifact
Explanation - Physical movement of leads can change electrode contact and introduce spikes or waves that mimic or obscure ECG signals.
Correct answer is: Motion artifact
Q.5 A 30‑Hz power line interference is present in an ECG recording. Which filter setting will best remove it?
High‑pass at 0.5 Hz
Notch at 50 Hz
Low‑pass at 40 Hz
Band‑stop from 25 Hz to 35 Hz
Explanation - A notch filter centered at the power line frequency (50 Hz in many regions) removes that interference without affecting the ECG band (up to ~150 Hz).
Correct answer is: Notch at 50 Hz
Q.6 Which component of the ECG represents the atrial depolarization?
P wave
QRS complex
T wave
U wave
Explanation - The P wave reflects the depolarization of the atria, preceding the ventricular depolarization shown by the QRS complex.
Correct answer is: P wave
Q.7 What is the approximate duration of the QRS complex in a normal adult ECG?
0.06–0.08 seconds
0.10–0.12 seconds
0.14–0.18 seconds
0.20–0.24 seconds
Explanation - The QRS complex typically lasts 60–80 ms in a healthy adult, reflecting rapid ventricular depolarization.
Correct answer is: 0.06–0.08 seconds
Q.8 Which lead placement is used to obtain a superior view of the heart?
Lead V1
Lead V6
Lead I
Lead III
Explanation - Lead V1 is placed in the 4th intercostal space at the right sternal border, giving a superior (or anterior) view of the heart.
Correct answer is: Lead V1
Q.9 A patient’s ECG shows a prolonged QT interval. Which of the following is a potential risk?
Atrial fibrillation
Torsades de pointes
Ventricular tachycardia
Bradycardia
Explanation - A prolonged QT interval predisposes to the polymorphic ventricular tachycardia known as torsades de pointes, which can be life‑threatening.
Correct answer is: Torsades de pointes
Q.10 Which electrode configuration is used for Lead II?
Right arm to left leg
Left arm to left leg
Right arm to left arm
Right leg to left leg
Explanation - Lead II records the potential difference between the right arm (positive) and the left leg (negative).
Correct answer is: Right arm to left leg
Q.11 What is the purpose of a differential amplifier in an ECG system?
Increase signal amplitude
Reduce common‑mode noise
Generate power line interference
Measure heart rate directly
Explanation - Differential amplifiers compare two input signals, cancelling out noise that is common to both (common‑mode), improving signal quality.
Correct answer is: Reduce common‑mode noise
Q.12 Which of the following is NOT a typical characteristic of an ECG lead?
Precordial leads
Augmented leads
Unipolar leads
Bipolar leads
Explanation - All standard ECG leads (I, II, III, aVR, aVL, aVF, V1–V6) are unipolar or bipolar; the term ‘unipolar’ refers to the measurement method rather than a lead type.
Correct answer is: Unipolar leads
Q.13 Which artifact is commonly caused by the patient’s breathing?
Baseline wander
Muscle artifact
Power line interference
Motion artifact
Explanation - Respiratory motion changes electrode impedance and shifts the baseline of the ECG, resulting in a slow drift over time.
Correct answer is: Baseline wander
Q.14 In a standard 12‑lead ECG, which lead displays the heart’s electrical activity from a lateral view?
Lead I
Lead III
Lead aVL
Lead V6
Explanation - Lead aVL provides a lateral perspective of the heart, looking at the left side from a slightly anterior direction.
Correct answer is: Lead aVL
Q.15 A sudden spike in an ECG recording is most likely caused by which of the following?
Power line interference
High‑pass filtering
Muscle artifact
Low‑pass filtering
Explanation - Power line noise (50/60 Hz) often appears as a sharp sinusoidal spike on the ECG trace if not filtered out.
Correct answer is: Power line interference
Q.16 What is the approximate bandwidth of a typical ECG signal?
0.05–100 Hz
0.5–150 Hz
5–500 Hz
50–500 Hz
Explanation - Most ECG instrumentation uses a bandwidth of 0.5 to 150 Hz to capture all clinically relevant waveform components.
Correct answer is: 0.5–150 Hz
Q.17 Which of the following is a common cause of an absent QRS complex?
Electrode misplacement
Lead disconnection
High‑pass filter set too high
Power line interference
Explanation - If a lead is disconnected, it will show no QRS complex because no electrical signal is received from the heart.
Correct answer is: Lead disconnection
Q.18 Which ECG lead is most sensitive to changes in right ventricular conduction?
Lead I
Lead V1
Lead V6
Lead aVL
Explanation - Lead V1 is placed on the right side of the sternum and is particularly sensitive to right ventricular activity.
Correct answer is: Lead V1
Q.19 A 12‑lead ECG uses how many electrode pairs for recording?
3
4
5
6
Explanation - The 12‑lead ECG uses 10 limb electrodes (4 limb and 6 precordial) resulting in 4 electrode pairs (R‑L, R‑A, L‑A, L‑R).
Correct answer is: 4
Q.20 Which of the following is the best way to reduce motion artifact in a pediatric ECG?
Use stronger electrodes
Increase gain
Secure electrodes with adhesive and compress the skin
Lower sampling rate
Explanation - Proper skin preparation and firm attachment reduce electrode motion, minimizing artifacts in pediatric recordings.
Correct answer is: Secure electrodes with adhesive and compress the skin
Q.21 Which of the following best describes the T wave?
Represents atrial depolarization
Represents ventricular repolarization
Represents ventricular depolarization
Represents atrial repolarization
Explanation - The T wave follows the QRS complex and indicates the repolarization of the ventricles.
Correct answer is: Represents ventricular repolarization
Q.22 What is the standard time interval for measuring the QT interval on an ECG?
From the start of the QRS to the end of the T wave
From the start of the P wave to the end of the T wave
From the end of the QRS to the end of the T wave
From the start of the Q wave to the start of the T wave
Explanation - The QT interval covers the entire period of ventricular depolarization and repolarization, starting at the QRS onset and ending at the T wave’s end.
Correct answer is: From the start of the QRS to the end of the T wave
Q.23 Which factor primarily determines the amplitude of the ECG signal?
Patient’s age
Lead placement
Heart muscle mass and position
Sampling rate
Explanation - The electrical activity of the heart’s muscle fibers and their orientation relative to electrodes primarily sets the signal amplitude.
Correct answer is: Heart muscle mass and position
Q.24 Why is a low‑pass filter with a cutoff of 150 Hz used in ECG instrumentation?
To remove baseline wander
To eliminate high‑frequency muscle artifacts
To preserve the QRS complex while rejecting higher‑frequency noise
To amplify the ECG signal
Explanation - The QRS complex contains frequencies up to about 100–150 Hz; a low‑pass filter above this preserves the signal while rejecting unwanted high‑frequency noise.
Correct answer is: To preserve the QRS complex while rejecting higher‑frequency noise
Q.25 Which component of a standard ECG circuit is responsible for amplifying the small bioelectric signal?
Differential amplifier
Integrator
Oscillator
Voltage divider
Explanation - A differential amplifier boosts the small voltage differences between electrodes while rejecting common noise, producing a usable ECG trace.
Correct answer is: Differential amplifier
Q.26 Which lead is most useful for detecting anterior wall myocardial infarction?
Lead V1
Lead V5
Lead II
Lead aVL
Explanation - Lead V1 provides a view of the anterior wall; abnormalities here often indicate anterior myocardial infarction.
Correct answer is: Lead V1
Q.27 Which of the following is a common source of high‑frequency noise in an ECG system?
Breathing
Electromagnetic interference from nearby electronics
Low‑pass filter
Power supply ripple
Explanation - High‑frequency electromagnetic interference from devices such as cell phones or radios can introduce noise in the ECG bandwidth.
Correct answer is: Electromagnetic interference from nearby electronics
Q.28 What does the PR interval represent?
Time from atrial to ventricular depolarization
Time from ventricular depolarization to repolarization
Time from atrial repolarization to ventricular depolarization
Time from the beginning of the QRS complex to the end of the T wave
Explanation - The PR interval measures the conduction time through the AV node and His‑Purkinje system from the onset of atrial depolarization to the start of ventricular depolarization.
Correct answer is: Time from atrial to ventricular depolarization
Q.29 Which artifact is commonly caused by a patient’s tremor during ECG recording?
Baseline wander
Motion artifact
Muscle artifact
Power line interference
Explanation - Tremors cause rapid, small movements of electrodes, producing spurious waves that overlay the true ECG signal.
Correct answer is: Motion artifact
Q.30 What is the purpose of a common‑mode rejection ratio (CMRR) in ECG amplifiers?
To increase signal gain
To reduce common‑mode noise
To adjust the sampling frequency
To provide power to electrodes
Explanation - A high CMRR ensures that noise present on both input lines is canceled out, improving the quality of the ECG signal.
Correct answer is: To reduce common‑mode noise
Q.31 Which lead configuration is used to view the heart’s electrical activity from a left‑sided perspective?
Lead aVR
Lead aVL
Lead aVF
Lead II
Explanation - Lead aVL provides a left‑sided view, with positive electrode on the left arm and negative on the right arm.
Correct answer is: Lead aVL
Q.32 In an ECG recording, which waveform component is typically the shortest in duration?
P wave
QRS complex
T wave
U wave
Explanation - The P wave is usually brief (80–100 ms), shorter than the QRS complex (60–80 ms) and T wave (160–200 ms).
Correct answer is: P wave
Q.33 Which of the following is a valid reason for using a 3‑lead ECG instead of a 12‑lead ECG?
Limited space in a wearable device
Requirement for full body mapping
Need for detailed atrial activity
Higher diagnostic accuracy
Explanation - 3‑lead ECGs are compact and suitable for portable or wearable monitors, sacrificing diagnostic detail for convenience.
Correct answer is: Limited space in a wearable device
Q.34 Which frequency band contains most of the ECG’s clinically relevant information?
0–1 Hz
1–20 Hz
20–200 Hz
200–500 Hz
Explanation - The primary ECG signals (P, QRS, T, U) reside within 1–20 Hz, with higher frequencies carrying noise and muscle artifacts.
Correct answer is: 1–20 Hz
Q.35 What is the most common source of high‑frequency noise that can mask the QRS complex?
Power line interference
Baseline wander
Muscle artifact
Low‑pass filtering
Explanation - Muscle (EMG) activity often produces high‑frequency noise that can obscure the sharp QRS complex if not adequately filtered.
Correct answer is: Muscle artifact
Q.36 Which of the following best describes the U wave?
Represents atrial repolarization
Represents ventricular repolarization
Represents late ventricular repolarization or Purkinje fibers
Represents muscle artifact
Explanation - The U wave follows the T wave and is believed to represent repolarization of the Purkinje system or late ventricular activity.
Correct answer is: Represents late ventricular repolarization or Purkinje fibers
Q.37 Which filter type is best suited for eliminating power line interference while preserving ECG morphology?
High‑pass filter
Notch filter
Low‑pass filter
Band‑stop filter from 0.5 Hz to 150 Hz
Explanation - A notch filter centered at the interference frequency (50/60 Hz) selectively removes that frequency without affecting other ECG components.
Correct answer is: Notch filter
Q.38 What is the typical sampling rate for modern digital ECG systems?
250 samples per second
500 samples per second
1000 samples per second
2000 samples per second
Explanation - A 500 Hz sampling rate provides adequate resolution to capture QRS complexes and preserves signal fidelity per the Nyquist criterion.
Correct answer is: 500 samples per second
Q.39 Which component of an ECG pre‑amplifier is responsible for maintaining a high input impedance?
High‑pass filter
Differential amplifier
Buffer amplifier
Integrator
Explanation - A buffer amplifier provides a high input impedance to avoid loading the electrodes and ensures accurate signal capture.
Correct answer is: Buffer amplifier
Q.40 Which of the following leads is best suited for detecting inferior wall myocardial infarction?
Lead I
Lead V4
Lead II
Lead V6
Explanation - Lead II, along with lead aVF, monitors the inferior wall of the heart, making it useful for detecting inferior infarctions.
Correct answer is: Lead II
Q.41 Which of these is NOT a typical characteristic of an ECG recording?
P wave precedes the QRS complex
QT interval is fixed across all beats
QRS complex is usually the tallest wave
T wave follows the QRS complex
Explanation - The QT interval varies with heart rate and other physiological conditions; it is not fixed.
Correct answer is: QT interval is fixed across all beats
Q.42 Which of the following is a primary function of the low‑pass filter in an ECG system?
To remove baseline drift
To limit high‑frequency noise
To increase ECG amplitude
To reduce power consumption
Explanation - The low‑pass filter cuts off frequencies above a specified limit, thereby reducing high‑frequency noise while preserving essential ECG components.
Correct answer is: To limit high‑frequency noise
Q.43 Which of the following best explains why a high CMRR is crucial in a noisy clinical environment?
It increases the gain of the ECG signal
It reduces the effect of common‑mode noise from power sources
It speeds up the sampling rate
It improves electrode adhesion
Explanation - A high CMRR ensures that common-mode noise, such as 50/60 Hz interference, is minimized, improving signal fidelity.
Correct answer is: It reduces the effect of common‑mode noise from power sources
Q.44 Which ECG lead is most affected by the presence of a left bundle branch block?
Lead V1
Lead V6
Lead II
Lead aVR
Explanation - Lead V1 is placed near the right ventricle; left bundle branch block often produces characteristic changes in V1, including a broad R wave.
Correct answer is: Lead V1
Q.45 What is the most appropriate method to minimize baseline wander in an ECG?
Increase the sampling rate
Use a high‑pass filter around 0.5 Hz
Apply a low‑pass filter at 150 Hz
Add a notch filter at 50 Hz
Explanation - A high‑pass filter at about 0.5 Hz removes low‑frequency baseline drift without affecting the ECG’s waveform.
Correct answer is: Use a high‑pass filter around 0.5 Hz
Q.46 Which of the following is a characteristic of the R wave in Lead II?
It is always negative
It is the largest deflection in the QRS complex
It occurs before the P wave
It is not visible in Lead II
Explanation - In Lead II, the R wave typically represents the most prominent depolarization of the ventricles and is the largest component of the QRS.
Correct answer is: It is the largest deflection in the QRS complex
Q.47 What is the effect of using a differential amplifier with a low CMRR on ECG quality?
Increased signal gain
Reduced noise from common sources
Increased susceptibility to common‑mode noise
Better artifact suppression
Explanation - A low CMRR fails to reject common‑mode interference, degrading ECG signal quality.
Correct answer is: Increased susceptibility to common‑mode noise
Q.48 Which artifact is most likely to be observed if a patient’s hand is touching an external metal surface during an ECG?
Power line interference
Muscle artifact
Motion artifact
Electrical noise from the metal contact
Explanation - Touching a metal surface can introduce high‑frequency noise due to capacitive coupling between the body and the metal.
Correct answer is: Electrical noise from the metal contact
Q.49 In an ECG signal, which part represents the ventricles’ recovery phase?
Q wave
R wave
T wave
U wave
Explanation - The T wave indicates the repolarization (recovery) phase of the ventricles after depolarization.
Correct answer is: T wave
Q.50 Which type of ECG lead uses a single electrode as a reference for all other electrodes?
Precordial leads
Limb leads
Augmented leads
Differential leads
Explanation - Precordial leads (V1–V6) use a single reference electrode (often the right leg) for all six leads, while limb leads use pairs.
Correct answer is: Precordial leads
Q.51 What is the primary advantage of a digital ECG over an analog one?
Higher signal amplitude
Longer lead placement time
Improved noise rejection and data storage
Lower cost of electrodes
Explanation - Digital systems can filter, store, and analyze ECG data more effectively, providing higher fidelity and ease of sharing.
Correct answer is: Improved noise rejection and data storage
Q.52 Which of the following best describes a 'flat T wave' in an ECG?
Indicates atrial fibrillation
Suggests hyperkalemia
Reflects a normal repolarization
Indicates a low amplitude ventricular repolarization
Explanation - A flattened T wave often signifies diminished ventricular repolarization, potentially due to electrolyte imbalances or ischemia.
Correct answer is: Indicates a low amplitude ventricular repolarization
Q.53 Which of the following is a key consideration when designing a wearable ECG monitor?
Large electrode area
High sampling rate (10 kHz)
Low power consumption
Complex lead configuration
Explanation - Wearables require power‑efficient designs to maintain battery life while providing adequate ECG fidelity.
Correct answer is: Low power consumption
Q.54 Which type of filter is most effective at eliminating 60 Hz interference without affecting ECG signals?
High‑pass filter
Low‑pass filter
Notch filter
Band‑stop filter from 20 Hz to 30 Hz
Explanation - A notch filter tuned to 60 Hz selectively removes this specific interference while preserving all other ECG components.
Correct answer is: Notch filter
Q.55 A patient with a pacemaker is undergoing an ECG. Which lead placement is safest?
Standard limb leads
Precordial leads only
No leads; use a device specific to pacemaker
Only leads that avoid the pacemaker generator area
Explanation - Lead placement should avoid direct contact with the pacemaker generator to prevent interference and patient discomfort.
Correct answer is: Only leads that avoid the pacemaker generator area
Q.56 Which parameter of the QRS complex is most used to assess ventricular hypertrophy?
R wave amplitude
Q wave depth
QT interval
T wave morphology
Explanation - Increased R wave amplitude, particularly in leads V5–V6, may indicate left ventricular hypertrophy.
Correct answer is: R wave amplitude
Q.57 Which of the following leads is considered a 'ventricular lead'?
Lead I
Lead aVR
Lead V1
Lead II
Explanation - Lead V1 is a precordial (ventricular) lead that views the anterior part of the heart’s ventricular activity.
Correct answer is: Lead V1
Q.58 Which of the following statements about the U wave is correct?
It is always present and prominent
It is due to atrial repolarization
It is usually absent in healthy adults
It is a normal part of ventricular repolarization
Explanation - The U wave can be absent in healthy individuals; its presence may indicate electrolyte abnormalities or ischemia.
Correct answer is: It is usually absent in healthy adults
Q.59 Which component of an ECG signal is most affected by the lead impedance mismatch?
Baseline drift
High‑frequency noise
Low‑frequency drift
Signal amplitude
Explanation - Impedance mismatch can attenuate the voltage difference between electrodes, reducing the amplitude of the recorded ECG.
Correct answer is: Signal amplitude
Q.60 What is the primary function of the pre‑amplifier in an ECG chain?
To filter out noise
To amplify the low‑amplitude bioelectric signal
To digitize the signal
To power the electrodes
Explanation - Pre‑amplifiers boost the tiny potentials (microvolts) from the heart to a level suitable for further processing.
Correct answer is: To amplify the low‑amplitude bioelectric signal
Q.61 Which of the following lead pairs would provide a right‑sided view of the heart?
Lead I
Lead V5
Lead aVL
Lead aVR
Explanation - Lead aVR views the heart from a right‑sided perspective, with its positive electrode on the right arm.
Correct answer is: Lead aVR
Q.62 A patient has a prolonged PR interval. Which condition is most likely?
First‑degree AV block
Right bundle branch block
Ventricular tachycardia
Sinus tachycardia
Explanation - A prolonged PR interval indicates delayed conduction through the AV node, characteristic of first‑degree atrioventricular block.
Correct answer is: First‑degree AV block
Q.63 What is the recommended electrode placement for Lead V5?
Left mid‑clavicular line, 5th intercostal space
Right mid‑clavicular line, 5th intercostal space
Left mid‑clavicular line, 4th intercostal space
Right mid‑clavicular line, 4th intercostal space
Explanation - Lead V5 is placed at the left mid‑clavicular line in the 5th intercostal space, providing a view of the left ventricle.
Correct answer is: Left mid‑clavicular line, 5th intercostal space
Q.64 Which ECG artifact is caused by rapid patient movement during an exercise test?
Baseline wander
Power line interference
Motion artifact
High‑pass filter distortion
Explanation - Rapid movement disrupts electrode contact, generating spurious spikes that overlay the ECG signal.
Correct answer is: Motion artifact
Q.65 Which of the following best explains why the ECG is recorded with a negative electrode on the right leg?
To serve as a reference for the other leads
To increase signal amplitude
To reduce the common‑mode noise
To act as the ground
Explanation - The right‑leg electrode acts as the common reference or ground for all limb leads, stabilizing the signal.
Correct answer is: To serve as a reference for the other leads
Q.66 Which type of filter would best isolate the QRS complex while reducing baseline drift and muscle noise?
High‑pass 0.5 Hz, low‑pass 150 Hz
Notch 50 Hz only
Band‑stop 0.5–150 Hz
Low‑pass 5 Hz only
Explanation - A band‑pass (0.5–150 Hz) filter removes both low‑frequency drift and high‑frequency noise, preserving the QRS complex.
Correct answer is: High‑pass 0.5 Hz, low‑pass 150 Hz
Q.67 Which lead orientation gives a view of the heart’s electrical activity from the left side?
Lead aVR
Lead aVL
Lead aVF
Lead V2
Explanation - Lead aVL looks from the left side, with the positive electrode on the left arm and negative on the right arm.
Correct answer is: Lead aVL
Q.68 What is the typical shape of a normal QRS complex?
Large single spike
Small spike followed by a notch
Triple deflection (Q, R, S)
Flat line
Explanation - A normal QRS consists of a Q wave (negative), an R wave (positive), and an S wave (negative) in that sequence.
Correct answer is: Triple deflection (Q, R, S)
Q.69 Which factor most directly determines the ECG signal’s amplitude?
Lead impedance
Electrode size
Heart muscle mass
Sampling rate
Explanation - The size of the heart’s muscular mass influences the magnitude of the electrical fields detected by electrodes.
Correct answer is: Heart muscle mass
Q.70 Which of the following leads is most useful for diagnosing left ventricular dysfunction?
Lead V1
Lead V5
Lead II
Lead aVR
Explanation - Lead V5, placed on the left lateral chest wall, is sensitive to changes in the left ventricle’s depolarization and repolarization.
Correct answer is: Lead V5
Q.71 Which component of the ECG is responsible for the repolarization of the ventricles?
P wave
QRS complex
T wave
U wave
Explanation - The T wave reflects the ventricular repolarization phase after the QRS complex.
Correct answer is: T wave
Q.72 What is the purpose of a 'buffer' stage in the ECG signal chain?
To increase signal amplitude
To provide a high input impedance
To filter out noise
To convert analog to digital
Explanation - The buffer stage isolates the electrodes from subsequent circuit stages, ensuring minimal loading and accurate signal capture.
Correct answer is: To provide a high input impedance
Q.73 Which artifact is most commonly caused by a patient’s breathing during ECG recording?
Baseline wander
Motion artifact
Power line interference
High‑frequency noise
Explanation - Respiratory motion changes electrode impedance, causing a low‑frequency baseline shift in the ECG trace.
Correct answer is: Baseline wander
Q.74 In a standard 12‑lead ECG, which lead provides a view from the posterior part of the heart?
Lead V1
Lead V5
Lead V6
Lead V7–V9 (if extended) but not in standard 12‑lead
Explanation - The standard 12‑lead ECG does not include posterior leads; extended leads V7–V9 are used for posterior assessment.
Correct answer is: Lead V7–V9 (if extended) but not in standard 12‑lead
Q.75 Which of the following best explains why high‑pass filtering is applied in ECG instrumentation?
To amplify high‑frequency muscle noise
To remove baseline drift
To suppress power line interference
To increase the QRS amplitude
Explanation - High‑pass filtering eliminates slow baseline variations, ensuring the ECG waveform remains centered.
Correct answer is: To remove baseline drift
Q.76 What is the typical frequency of a normal ECG signal’s QRS complex?
0.05–1 Hz
1–5 Hz
5–50 Hz
50–200 Hz
Explanation - The QRS complex contains energy mainly in the 5–50 Hz band, reflecting rapid ventricular depolarization.
Correct answer is: 5–50 Hz
Q.77 Which of the following is a common source of 60 Hz interference in an ECG recording?
Patient breathing
Power supply line
Electrode motion
Low‑pass filter
Explanation - The mains electrical supply operates at 60 Hz, injecting sinusoidal interference into the ECG trace.
Correct answer is: Power supply line
Q.78 Which of the following leads is best suited for detecting arrhythmias that involve the left atrium?
Lead I
Lead II
Lead aVL
Lead V4
Explanation - Lead aVL provides a lateral view of the left atrium, making it useful for identifying atrial arrhythmias.
Correct answer is: Lead aVL
Q.79 Which type of filter will reduce both high‑frequency noise and baseline drift simultaneously?
High‑pass filter
Low‑pass filter
Band‑pass filter
Notch filter
Explanation - A band‑pass filter allows frequencies within a specified range to pass while attenuating both low and high frequency components.
Correct answer is: Band‑pass filter
Q.80 What is the purpose of the right‑leg drive (RLD) circuit in ECG instrumentation?
To drive the signal amplitude higher
To supply a common reference voltage
To amplify the ECG signal
To measure the heart’s electrical activity
Explanation - The RLD circuit provides a stable reference to reduce noise and common‑mode voltage across all electrodes.
Correct answer is: To supply a common reference voltage
Q.81 Which artifact is most likely seen as a slow oscillation that follows the patient’s respiration rate?
Baseline wander
Power line interference
Motion artifact
High‑frequency noise
Explanation - Baseline wander is often directly related to breathing, producing a slow sinusoidal fluctuation in the ECG trace.
Correct answer is: Baseline wander
Q.82 Which ECG lead orientation corresponds to the heart’s electrical axis when looking from the left side?
Lead aVR
Lead aVL
Lead aVF
Lead V2
Explanation - Lead aVL looks at the heart from the left side; it provides a view of the electrical axis from that perspective.
Correct answer is: Lead aVL
Q.83 Which of the following best describes the shape of the P wave in a normal ECG?
A small, positive deflection
A large, negative deflection
A flat line
A double hump
Explanation - The P wave is typically a small, upright (positive) deflection representing atrial depolarization.
Correct answer is: A small, positive deflection
Q.84 What is the main reason for using a 12‑lead ECG in clinical practice?
To increase signal amplitude
To reduce noise
To provide a comprehensive view of heart activity from multiple angles
To simplify the electrode placement
Explanation - The 12‑lead ECG captures the heart’s electrical activity from multiple perspectives, facilitating diagnosis.
Correct answer is: To provide a comprehensive view of heart activity from multiple angles
Q.85 Which of the following is NOT a typical ECG artifact?
Baseline wander
Power line interference
Motion artifact
Signal amplification
Explanation - Signal amplification is an intended function of the instrumentation, not an artifact that contaminates the ECG.
Correct answer is: Signal amplification
Q.86 What is the effect of using a low‑pass filter with a cutoff frequency of 40 Hz on a normal ECG?
It eliminates baseline drift
It removes all QRS complex information
It preserves the QRS complex and removes high‑frequency noise
It amplifies the T wave
Explanation - A 40 Hz low‑pass filter keeps most ECG information while reducing high‑frequency noise like EMG.
Correct answer is: It preserves the QRS complex and removes high‑frequency noise
Q.87 Which of the following is a key consideration for designing a high‑frequency ECG amplifier?
Low input impedance
High CMRR
High noise figure
Low sampling rate
Explanation - A high CMRR ensures that common‑mode noise is suppressed, critical for high‑frequency fidelity.
Correct answer is: High CMRR
Q.88 Which of the following is a hallmark ECG finding in left bundle branch block?
ST‑segment elevation in leads V1 and V2
Wide QRS complex with a delayed R wave in V5‑V6
Shortened PR interval
Negative T waves in V1‑V3
Explanation - Left bundle branch block shows a wide QRS and delayed R wave in the lateral precordial leads.
Correct answer is: Wide QRS complex with a delayed R wave in V5‑V6
Q.89 What is the main advantage of using a notch filter at 60 Hz in a standard ECG?
To increase sampling rate
To eliminate power line interference while preserving other frequencies
To reduce baseline wander
To amplify the QRS complex
Explanation - A notch filter selectively removes the 60 Hz interference without affecting the rest of the ECG spectrum.
Correct answer is: To eliminate power line interference while preserving other frequencies
Q.90 Which of the following best describes the S wave?
The first negative deflection of the QRS complex
The first positive deflection of the QRS complex
The final positive deflection of the QRS complex
The wave following the QRS complex
Explanation - The S wave is the negative deflection following the R wave in the QRS complex.
Correct answer is: The first negative deflection of the QRS complex
Q.91 Which of the following best explains the purpose of the 'ground' electrode in an ECG?
To measure the heart's electrical activity
To provide a reference point and reduce noise
To amplify the ECG signal
To increase electrode impedance
Explanation - The ground electrode provides a common reference, helping cancel out interference and stabilize the signal.
Correct answer is: To provide a reference point and reduce noise
Q.92 In a 12‑lead ECG, which lead is considered the 'right‑sided' lead?
Lead I
Lead aVR
Lead II
Lead aVF
Explanation - Lead aVR looks at the heart from a right‑sided perspective, with its positive electrode on the right arm.
Correct answer is: Lead aVR
Q.93 Which ECG lead placement is most useful for detecting anterior wall myocardial infarction?
Lead V1
Lead V4
Lead V6
Lead II
Explanation - Lead V4 sits on the left mid‑clavicular line, 4th intercostal space, and is optimal for visualizing the anterior wall.
Correct answer is: Lead V4
Q.94 What is the most common source of 50 Hz interference in ECG recordings in Europe?
Power line interference
Electrode motion
Muscle artifact
High‑pass filter distortion
Explanation - The European mains supply runs at 50 Hz, which can couple into ECG signals if not filtered.
Correct answer is: Power line interference
Q.95 Which of the following statements best describes the P wave?
It represents ventricular depolarization
It reflects atrial repolarization
It indicates atrial depolarization
It shows ventricular repolarization
Explanation - The P wave corresponds to the atria depolarizing before the ventricles.
Correct answer is: It indicates atrial depolarization
Q.96 What is a major advantage of a digital ECG system over an analog system?
Higher signal amplitude
Better artifact rejection and storage
Simpler electrode placement
Lower cost of electrodes
Explanation - Digital systems allow precise filtering, storage, and analysis of ECG data, improving diagnostic capability.
Correct answer is: Better artifact rejection and storage
Q.97 Which of the following is a typical characteristic of an ECG lead V6?
Placed on the right mid‑clavicular line, 6th intercostal space
Placed on the left mid‑clavicular line, 6th intercostal space
Placed on the right mid‑clavicular line, 4th intercostal space
Placed on the left mid‑clavicular line, 4th intercostal space
Explanation - Lead V6 is positioned at the left mid‑clavicular line in the 6th intercostal space, giving a left‑lateral view.
Correct answer is: Placed on the left mid‑clavicular line, 6th intercostal space
Q.98 Which component of the ECG system is primarily responsible for rejecting common‑mode noise?
Pre‑amplifier
Differential amplifier
Buffer amplifier
Integrator
Explanation - The differential amplifier measures the voltage difference between two electrodes, canceling noise common to both inputs.
Correct answer is: Differential amplifier
Q.99 Which artifact is often seen as a small, regular ripple on the ECG trace?
Baseline wander
Power line interference
Muscle artifact
Motion artifact
Explanation - The mains frequency (50/60 Hz) appears as a regular ripple, which can be mitigated with a notch filter.
Correct answer is: Power line interference
Q.100 Which of the following is NOT a typical reason for a prolonged QT interval?
Hyperkalemia
Hypothyroidism
Use of certain antiarrhythmic drugs
Hypocalcemia
Explanation - While various factors can prolong the QT, hypothyroidism is not typically associated with a prolonged QT interval.
Correct answer is: Hypothyroidism
Q.101 What is the typical width of a normal QRS complex in milliseconds?
50–80 ms
80–100 ms
100–120 ms
120–150 ms
Explanation - A normal QRS complex lasts between 50 and 80 ms, reflecting the rapid ventricular depolarization.
Correct answer is: 50–80 ms
Q.102 Which of the following leads is most sensitive to detecting right‑ventricular abnormalities?
Lead V1
Lead V2
Lead V5
Lead V6
Explanation - Lead V1 is placed near the right ventricle; it is especially sensitive to right‑ventricular changes.
Correct answer is: Lead V1
Q.103 Which of the following best describes the U wave?
Represents atrial repolarization
Represents ventricular repolarization
Represents late repolarization of the Purkinje system
Represents muscle artifact
Explanation - The U wave follows the T wave and is believed to arise from late ventricular repolarization, often related to Purkinje fibers.
Correct answer is: Represents late repolarization of the Purkinje system
Q.104 Which of the following is a common source of muscle artifact in ECG recordings?
Electrode motion
Breathing
Muscle contraction
Power line interference
Explanation - Electrical activity from skeletal muscle contractions can produce high‑frequency noise that contaminates the ECG.
Correct answer is: Muscle contraction
Q.105 What is the purpose of a high‑pass filter with a cutoff frequency of 0.5 Hz in ECG instrumentation?
To block the QRS complex
To remove low‑frequency baseline drift
To eliminate high‑frequency noise
To increase the T wave amplitude
Explanation - A high‑pass filter at 0.5 Hz suppresses baseline drift while preserving the ECG waveform components.
Correct answer is: To remove low‑frequency baseline drift
Q.106 Which of the following leads is a 'right‑sided' lead in a 12‑lead ECG?
Lead I
Lead II
Lead aVR
Lead aVF
Explanation - Lead aVR looks at the heart from the right side; it has a positive electrode on the right arm.
Correct answer is: Lead aVR
Q.107 Which of the following best explains why a low‑pass filter is used in ECG signal processing?
To amplify low‑frequency signals
To reduce high‑frequency noise
To eliminate the QRS complex
To increase sampling rate
Explanation - The low‑pass filter removes frequencies above a set cutoff (e.g., 150 Hz), reducing EMG and other high‑frequency noise.
Correct answer is: To reduce high‑frequency noise
Q.108 What is the typical sampling interval for a standard ECG recorder with a 500 Hz sampling rate?
0.002 seconds
0.004 seconds
0.01 seconds
0.02 seconds
Explanation - Sampling at 500 Hz means 500 samples per second, so each sample is 1/500 s ≈ 0.002 s apart.
Correct answer is: 0.002 seconds
Q.109 Which of the following is a typical symptom of an abnormal ECG finding known as left bundle branch block?
Chest pain
Shortness of breath
Palpitations
All of the above
Explanation - Left bundle branch block can manifest with chest pain, dyspnea, or palpitations, though many patients are asymptomatic.
Correct answer is: All of the above
Q.110 Which of the following lead placements is used to monitor the heart’s electrical activity from a left‑sided perspective?
Lead aVR
Lead aVL
Lead aVF
Lead V2
Explanation - Lead aVL is oriented leftwards, providing a view from the left side of the heart.
Correct answer is: Lead aVL
Q.111 What is the effect of using a high CMRR differential amplifier on ECG signals?
It amplifies common‑mode noise
It rejects common‑mode noise
It reduces the QRS amplitude
It increases power consumption
Explanation - A high CMRR means the amplifier effectively cancels out noise that is common to both inputs, improving signal quality.
Correct answer is: It rejects common‑mode noise
Q.112 Which of the following leads is best suited for detecting posterior wall myocardial infarction?
Lead V1
Lead V5
Lead V6
Extended leads V7–V9
Explanation - Standard 12‑lead ECG lacks posterior leads; V7–V9 are used specifically for posterior wall assessment.
Correct answer is: Extended leads V7–V9
Q.113 Which of the following statements accurately describes the T wave?
It follows the QRS complex and represents ventricular repolarization
It precedes the QRS complex and represents atrial repolarization
It is part of the QRS complex
It is a high‑frequency noise artifact
Explanation - The T wave is the waveform that follows QRS, indicating the ventricles returning to a resting state.
Correct answer is: It follows the QRS complex and represents ventricular repolarization
Q.114 What is the typical amplitude of the R wave in a normal ECG?
0.1–0.2 mV
0.2–0.4 mV
0.4–0.6 mV
0.6–1.0 mV
Explanation - The R wave in a normal adult ECG typically ranges between 0.4 and 0.6 mV.
Correct answer is: 0.4–0.6 mV
Q.115 Which of the following best explains the role of the 'ground' electrode in an ECG?
It directly records the heart’s electrical activity
It acts as a reference to reduce noise
It amplifies the signal
It measures body temperature
Explanation - The ground electrode provides a common reference, minimizing common‑mode interference in the ECG recording.
Correct answer is: It acts as a reference to reduce noise
Q.116 What is the effect of increasing the gain in an ECG pre‑amplifier?
It increases the signal amplitude
It reduces the baseline wander
It lowers the CMRR
It increases the sampling rate
Explanation - Higher gain boosts the small voltage from the heart, making the ECG trace more pronounced.
Correct answer is: It increases the signal amplitude
Q.117 Which of the following is NOT a standard limb lead in a 12‑lead ECG?
Lead I
Lead II
Lead III
Lead V1
Explanation - Lead V1 is a precordial (chest) lead, not a limb lead; limb leads include I, II, and III.
Correct answer is: Lead V1
Q.118 Which lead orientation corresponds to the heart’s electrical axis when looking from the left side?
Lead aVR
Lead aVL
Lead aVF
Lead V2
Explanation - Lead aVL provides a left‑sided view of the heart’s electrical axis.
Correct answer is: Lead aVL
Q.119 Which of the following is a major cause of the baseline shift seen in ECG traces?
Power line interference
Respiratory motion
High‑pass filtering
Low‑pass filtering
Explanation - Respiratory motion changes electrode impedance, causing a slow baseline shift known as baseline wander.
Correct answer is: Respiratory motion
Q.120 Which ECG lead provides a view from the posterior left ventricle?
Lead V1
Lead V6
Lead V5
Lead V7
Explanation - Lead V7, placed in the 7th intercostal space, gives a posterior view of the left ventricle.
Correct answer is: Lead V7
Q.121 Which filter type is most suitable for eliminating both low‑frequency baseline drift and high‑frequency noise in ECG signals?
High‑pass filter
Low‑pass filter
Band‑pass filter
Notch filter
Explanation - A band‑pass filter allows frequencies in a specified range (e.g., 0.5–150 Hz) while attenuating both low and high frequency components.
Correct answer is: Band‑pass filter
Q.122 Which of the following is a typical artifact seen as a repetitive wave at 50/60 Hz on an ECG?
Baseline wander
Motion artifact
Power line interference
Muscle artifact
Explanation - Power line interference appears as a regular 50/60 Hz ripple on the ECG trace.
Correct answer is: Power line interference
Q.123 What is the primary advantage of using a differential amplifier in an ECG system?
To amplify the signal
To reduce common‑mode noise
To increase sampling rate
To lower electrode impedance
Explanation - A differential amplifier subtracts two electrode signals, effectively canceling noise common to both inputs.
Correct answer is: To reduce common‑mode noise