Question

A wire ABCDEF (with each side of length L) is bent as shown in figure and carrying current I is placed in a uniform magnetic induction B parallel to positive y direction. What is the force experienced by the wire.

• A. BIL along y-axis
• B. 2BIL along z-axis
• C. BIL along z-axis
• D. 2BIL along y-axis.

Answer 1

Answer: (C)

Imagine a conductor link at AF so that a closed loop is formed. A closed loop in a uniform magnetic field has no net force. $\therefore$ F = 0 Let $F_c$ be the force on the given wire and $F_i$ be the force on imaginary wire F = F${}_c$ + F${}_i$ = 0 or Fc = - F${}_i$ But F${}_i$ = BIL sin $90^{\circ }$ = BIL along negative z-axis $(Flemin{g}^{\prime }sLefthandrule)$ $\therefore$ F${}_c$ = BIL along positive z-axis