Question

AB and CD are smooth parallel horizontal rails on which a conductor T can slide. A cell of emf E drives a current $i$ through the rails. Then

• A. the force on T is proportional to $i$
• B. the force on T is proportional to $i^2$
• C. if the direction of $i$ is reversed in the circuit by reversing $E$, the force on T will reverse in direction
• D. if the direction of $i$ is reversed in the circuit by reversing $E$, the force on T will remain in the same direction

Answer 1

Answer: (B), (D)

the force on T is proportional to $i^2$
if the direction of $i$ is reversed in the circuit by reversing $E$, the force on T will remain in the same direction

Currents in AB and CD causes the same magnetic field in upward direction on T and is proportional to $i$, hence, the force on T is proportional to $i^2$. If the direction of $i$ is reversed in the circuit by reversing $E$, the direction of magnetic field will reverse and the force on T will remain in the same direction