# Physics Questions and Answers – Magnetic Force

«
»

This set of Physics Multiple Choice Questions & Answers (MCQs) focuses on “Magnetic Force”.

1. What is the space around a current-carrying conductor, in which its magnetic effect can be experienced called?
a) Electric field
b) Magnetic pole
c) Magnetic field
d) Charge distribution

Explanation: The space around a current-carrying conductor, in which its magnetic effect can be experienced is called the magnetic field. When a current is passed through a conductor, it modifies the space around the conductor and forms a magnetic field.

2. Give the SI unit of the magnetic field.
a) Ampere
b) Tesla
c) Oersted
d) Weber

Explanation: The SI unit of the magnetic field is tesla, named after the great scientist Nikola tesla. 1 tesla is 107 times the magnetic field produced by a conducting wire of length one metre and carrying a current of one ampere at a distance of one metre from it and perpendicular to it.

3. What is the force exerted by a stationary charge when it is placed in a magnetic field?
a) Zero
b) Maximum
c) Minimum
d) Depends on the strength of the magnetic field

Explanation: A stationary charge does not produce any magnetic field and it does not suffer any interaction against the external magnetic field. Hence the force exerted is zero.

4. What is the work done by the magnetic field on a moving charged particle?
a) Maximum
b) Minimum
c) Depends on the strength of the magnetic field
d) Zero

Explanation: As the magnetic force acts in a direction perpendicular to the direction of the velocity or the direction of motion of the charged particle, so the work done is zero.
W = F × dl × cos 90°
W = 0.

5. The north pole of a magnet is brought near a stationary negatively charged conductor. What is the force experienced by it at the poles?
a) Maximum
b) Minimum
c) Zero
d) Depend on the nature of the conductor

Explanation: The north pole of a magnet will not experience any force. This is because a stationary charge does not produce any magnetic field. Therefore, the force experienced by the magnet at the poles is zero.

6. When a charge moves parallel or antiparallel to the direction of the magnetic field, it experiences a maximum force. State true or false.
a) True
b) False

Explanation: When a charge moves parallel or antiparallel to the direction of the magnetic field, it experiences a minimum (zero) force.
When θ = 0o or 180o,
Fm = qvBsinθ = qvB (0) = 0.

7. Identify the condition under which the force acting on a charge moving through a uniform magnetic field is minimum.
a) θ = 90o
b) θ = 180o
c) θ = 270o
d) θ = 340o

Explanation: When θ = 0o or 180o,
Fm = qvBsinθ = qvB (0) = 0.
So when a charge moves parallel or antiparallel to the direction of the magnetic field, it experiences a minimum force.

8. Identify the condition under which the force acting on a charge moving through a uniform magnetic field is maximum.
a) θ = 90o
b) θ = 180o
c) θ = 0o
d) θ = 360o

Explanation: When θ = 90o → Fm is maximum.
Thus a charge experiences a maximum force when it moves perpendicular to the direction of the magnetic field. So, this is the condition when the force experienced is maximum.

Sanfoundry Global Education & Learning Series – Physics – Class 12. 