Q.1 Which particle is the source of magnetic fields in matter?
Neutrons
Protons
Electrons
Positrons
Explanation - Electrons generate magnetic fields due to their intrinsic spin and orbital motion around the nucleus.
Correct answer is: Electrons
Q.2 The unit of magnetic flux is:
Tesla
Weber
Henry
Ampere-turn
Explanation - Magnetic flux is measured in Weber (Wb), defined as Tesla × m².
Correct answer is: Weber
Q.3 The magnetic field inside a long straight solenoid carrying current is:
Zero
Constant
Inversely proportional to length
Varies sinusoidally
Explanation - The field inside a long solenoid is uniform and proportional to current and turns per unit length.
Correct answer is: Constant
Q.4 Magnetic lines of force:
Intersect each other
Form closed loops
Start from north pole and end at infinity
Are straight lines always
Explanation - Magnetic field lines always form continuous closed loops from the north to south pole outside the magnet and south to north inside.
Correct answer is: Form closed loops
Q.5 A charged particle enters a magnetic field perpendicular to its velocity. Its path will be:
Straight line
Parabolic
Circular
Elliptical
Explanation - The Lorentz force provides a centripetal force, making the particle move in a circular path.
Correct answer is: Circular
Q.6 The SI unit of magnetic field intensity (H) is:
Tesla
Ampere per meter
Weber per meter
Henry per meter
Explanation - Magnetic field intensity H is measured in Ampere-turns per meter (A/m).
Correct answer is: Ampere per meter
Q.7 What is the magnetic moment of a current loop proportional to?
Current × Area
Current / Area
Charge × Velocity
Area only
Explanation - Magnetic moment (M) = Current (I) × Area (A) of the loop.
Correct answer is: Current × Area
Q.8 The Earth's magnetic field is due to:
Atmosphere
Rotation of Earth
Molten iron currents in outer core
Gravitational pull
Explanation - Earth’s magnetic field arises from convection currents of molten iron and nickel in the outer core (geodynamo effect).
Correct answer is: Molten iron currents in outer core
Q.9 Which law explains the force on a current-carrying conductor in a magnetic field?
Coulomb’s Law
Faraday’s Law
Ampere’s Law
Lorentz Force Law
Explanation - The Lorentz force law defines the force experienced by charges or conductors in electromagnetic fields.
Correct answer is: Lorentz Force Law
Q.10 The north pole of a bar magnet is placed facing north. The force on it will be:
Attractive
Repulsive
Zero
Oscillatory
Explanation - Like poles repel. North of a magnet faces Earth’s north magnetic pole (geographically south).
Correct answer is: Repulsive
Q.11 Which material is strongly attracted by a magnet?
Copper
Aluminium
Iron
Wood
Explanation - Iron is ferromagnetic and strongly attracted by magnets.
Correct answer is: Iron
Q.12 The relation between magnetic induction B and magnetic field intensity H in free space is:
B = μ0H
B = H/μ0
B = μH²
B = μ/H
Explanation - In free space, magnetic flux density B = μ0 × H, where μ0 is permeability of free space.
Correct answer is: B = μ0H
Q.13 If a soft iron core is introduced in a solenoid, the magnetic field inside:
Remains same
Decreases
Increases
Becomes zero
Explanation - Soft iron increases magnetic flux due to its high permeability.
Correct answer is: Increases
Q.14 Magnetism in materials is mainly due to:
Nuclear spin
Electron spin
Neutron mass
Proton charge
Explanation - Magnetism originates from the spin and orbital motion of electrons.
Correct answer is: Electron spin
Q.15 The magnetic force on a stationary charge is:
Maximum
Minimum
Zero
Infinite
Explanation - Magnetic force requires motion; for v = 0, F = q(v × B) = 0.
Correct answer is: Zero
Q.16 The direction of force on a moving charge in a magnetic field is given by:
Coulomb’s law
Right-hand rule
Fleming’s left-hand rule
Gauss’s law
Explanation - The right-hand rule gives direction of force (perpendicular to velocity and field).
Correct answer is: Right-hand rule
Q.17 Magnetic permeability of free space (μ0) is:
4π × 10⁻⁷ H/m
9 × 10⁹ N·m²/C²
8.85 × 10⁻¹² C²/N·m²
1.6 × 10⁻¹⁹ C
Explanation - Permeability of free space is a fundamental constant μ0 = 4π × 10⁻⁷ H/m.
Correct answer is: 4π × 10⁻⁷ H/m
Q.18 Magnetic susceptibility (χ) is:
Dimensionless
Has units of Tesla
Same as permeability
Same as conductivity
Explanation - Magnetic susceptibility is dimensionless, as it is a ratio of magnetization to field intensity.
Correct answer is: Dimensionless
Q.19 Which law states that the line integral of magnetic field around a closed path equals μ0 times current enclosed?
Faraday’s law
Gauss’s law
Ampere’s circuital law
Biot-Savart law
Explanation - Ampere’s law relates magnetic field around a loop to the total current through the loop.
Correct answer is: Ampere’s circuital law
Q.20 A magnetic needle freely suspended in a uniform magnetic field points:
East
West
North-South
Randomly
Explanation - Magnetic needle aligns with Earth’s magnetic field and points north-south.
Correct answer is: North-South
Q.21 Which type of material is weakly repelled by a magnetic field?
Ferromagnetic
Paramagnetic
Diamagnetic
Non-magnetic
Explanation - Diamagnetic materials are weakly repelled by external magnetic fields.
Correct answer is: Diamagnetic
Q.22 When a bar magnet is cut into two equal pieces along its length:
Each piece becomes a magnet
Poles disappear
Only one piece remains magnetic
Poles get separated
Explanation - Each fragment retains its own north and south poles.
Correct answer is: Each piece becomes a magnet
Q.23 The magnetic effect of current was discovered by:
Ampere
Oersted
Faraday
Tesla
Explanation - Hans Christian Oersted discovered that electric current produces a magnetic field.
Correct answer is: Oersted
Q.24 If current in a wire is doubled, magnetic field around it becomes:
Half
Double
Four times
Unchanged
Explanation - Magnetic field around a conductor is directly proportional to current.
Correct answer is: Double
Q.25 The direction of current in a solenoid that produces a north pole at its face is given by:
Fleming’s left-hand rule
Coulomb’s law
Right-hand thumb rule
Ampere’s law
Explanation - Curl the fingers in the direction of current; thumb points towards the north pole.
Correct answer is: Right-hand thumb rule