Q.1 Ohm’s law relates current with which of the following quantities?
Voltage and resistance
Capacitance and inductance
Charge and time
Power and energy
Explanation - Ohm’s law states that current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance (I = V/R).
Correct answer is: Voltage and resistance
Q.2 The SI unit of resistivity is:
Ω·m
Ω/m
Ω·m²
Ω⁻¹·m
Explanation - Resistivity (ρ) is defined as R·A/L, where R is resistance, A is cross-sectional area, and L is length. The unit is ohm-metre (Ω·m).
Correct answer is: Ω·m
Q.3 When a copper wire is stretched to double its length, its resistance becomes:
Doubled
Halved
Four times
Unchanged
Explanation - Resistance R = ρL/A. Stretching doubles length (L→2L) and reduces area (A→A/2), hence R = 4R₀.
Correct answer is: Four times
Q.4 The drift velocity of electrons in a conductor is of the order of:
10⁻⁴ m/s
10⁻² m/s
10² m/s
10⁶ m/s
Explanation - Though current appears instantaneous, individual electron drift velocities are extremely small (~10⁻⁴ m/s).
Correct answer is: 10⁻⁴ m/s
Q.5 Which of the following materials is an insulator?
Copper
Aluminum
Glass
Iron
Explanation - Insulators do not allow current to pass easily. Glass is a good electrical insulator.
Correct answer is: Glass
Q.6 What is the reciprocal of resistance called?
Capacitance
Inductance
Conductance
Reactance
Explanation - Conductance G is defined as the reciprocal of resistance (G = 1/R).
Correct answer is: Conductance
Q.7 In a metallic conductor, current is due to:
Motion of free electrons
Protons moving
Neutrons moving
All of the above
Explanation - In metals, conduction is due to the drift of free electrons while the positive ions remain fixed.
Correct answer is: Motion of free electrons
Q.8 Which instrument is used to measure electric current?
Voltmeter
Ammeter
Galvanometer
Potentiometer
Explanation - Ammeter is connected in series to measure electric current in amperes.
Correct answer is: Ammeter
Q.9 The unit of electric current is:
Coulomb
Volt
Ampere
Ohm
Explanation - Ampere is defined as one coulomb of charge flowing per second.
Correct answer is: Ampere
Q.10 The resistance of a conductor depends on:
Length only
Area of cross-section only
Material only
Length, area and material
Explanation - R = ρL/A, so resistance depends on material (ρ), length (L), and cross-sectional area (A).
Correct answer is: Length, area and material
Q.11 Which law governs the combination of resistors in series and parallel?
Gauss’s law
Kirchhoff’s laws
Ampere’s law
Coulomb’s law
Explanation - Kirchhoff’s current law (KCL) and voltage law (KVL) are used to solve resistor networks.
Correct answer is: Kirchhoff’s laws
Q.12 When two resistors R1 and R2 are connected in parallel, the equivalent resistance is:
R1 + R2
R1R2/(R1+R2)
R1 − R2
R1/R2
Explanation - For parallel resistors, 1/Req = 1/R1 + 1/R2. Hence, Req = (R1R2)/(R1+R2).
Correct answer is: R1R2/(R1+R2)
Q.13 Which of the following does not affect the resistance of a conductor?
Temperature
Length
Cross-sectional area
Voltage applied
Explanation - Resistance is material property (depends on ρ, L, A, and T), not on applied voltage.
Correct answer is: Voltage applied
Q.14 In a series circuit, current is:
Different across components
Same through all components
Depends on resistance only
Zero
Explanation - In a series connection, the same current flows through all resistors.
Correct answer is: Same through all components
Q.15 What is the current through a 2 Ω resistor connected across a 10 V battery?
20 A
10 A
5 A
2 A
Explanation - Using Ohm’s law, I = V/R = 10/2 = 5 A.
Correct answer is: 5 A
Q.16 The heating effect of current is used in:
Electric bulb
Heater
Fuse
All of these
Explanation - Heat produced (H = I²Rt) is used in bulbs (filament heating), heaters, and fuses.
Correct answer is: All of these
Q.17 The work done in moving a charge of 2 C through a potential difference of 12 V is:
6 J
12 J
24 J
2 J
Explanation - Work W = qV = 2 × 12 = 24 J.
Correct answer is: 24 J
Q.18 The internal resistance of an ideal cell is:
Very high
Zero
Infinity
Variable
Explanation - An ideal cell is assumed to have no internal resistance, hence maximum current delivery.
Correct answer is: Zero
Q.19 Which physical quantity is measured in coulombs per second?
Charge
Potential
Current
Resistance
Explanation - 1 Coulomb/second = 1 Ampere = current.
Correct answer is: Current
Q.20 If resistance is doubled and voltage is kept constant, current becomes:
Double
Half
Same
Zero
Explanation - From Ohm’s law, I = V/R. If R doubles, I is halved.
Correct answer is: Half
Q.21 The resistance of a wire is proportional to:
L/A
A/L
L²
1/L
Explanation - R = ρL/A, directly proportional to length and inversely proportional to area.
Correct answer is: L/A
Q.22 What happens to resistance of most metals when temperature increases?
Increases
Decreases
Remains same
Becomes zero
Explanation - With temperature rise, lattice vibrations increase, making electron flow harder, so resistance increases.
Correct answer is: Increases
Q.23 In an electric circuit, potential difference is measured using:
Ammeter
Voltmeter
Ohmmeter
Galvanometer
Explanation - Voltmeter is always connected in parallel to measure potential difference.
Correct answer is: Voltmeter
Q.24 The power consumed in a resistor is maximum when:
Load resistance = 0
Load resistance = internal resistance
Load resistance is very high
Current is zero
Explanation - According to maximum power transfer theorem, P is maximum when external resistance equals internal resistance of source.
Correct answer is: Load resistance = internal resistance
Q.25 1 kilowatt-hour of electrical energy is equal to:
100 J
3600 J
3.6 × 10⁶ J
1 J
Explanation - 1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ J.
Correct answer is: 3.6 × 10⁶ J