Question

The force exerted on a current-carrying wire placed in a magnetic field is zero when the angle between the wire and the direction of magnetic field.
A. 180⁰
B. 90⁰
C. 60⁰
D. 15⁰

Answer 1

Hint: The force exerted on a current-carrying wire placed in a magnetic field is zero when a current-carrying conductor is parallel to the field.

Complete step by step solution:
For a current-carrying wire, force is felt in the presence of an external magnetic field. The magnetic force on a current in a magnetic field is expressed as
$F = BIL\sin \theta $
Here, F is the force
B is the flux density
I is the current
L is the length of the conductor
$\theta $ is the angle that current makes with the magnetic field
Force is maximum when $\theta $ is 90⁰ because $\sin {90^0}$= 1
Force is zero when the current is parallel to the field lines. $\theta $ is 0⁰ .
In vector form, $F = I\left( {L \times B} \right)$
The force depends on the angle between the vector B and the vector L in the direction.
In magnitude form, F=I*L*B*$\sin \theta $ ,
If theta is 180⁰ and 0⁰ then, the force is zero (sin180⁰=0)
We know that sin 180° is 0. Therefore, the force exerted on a current-carrying wire that is placed in a magnetic field is zero.
So, the angle is 180⁰.
So, the correct answer is “Option A”.

Note: If a charge is moved through a magnetic field at an angle, it will experience a force. According to Fleming Left hand’s rule for the direction of motion and the Right hand’s rule for the direction of motion.