Question

The force on a straight current-carrying wire in a magnetic field is proportional to the current in the wire, the strength of the field, and the _____ of the wire.
A) Make-up
B) Length
C) X-Section

Answer 1

magnetic force on a current carrying wire is given as

$F = i(L x B)$

$F = i L B sin\theta$

so it is proportional to

(i) current in the wire (i)

(ii) strength of magnetic field (B)

(iii) length of the wire (L)

so correct answer would be

B) Length