Q. An axle of truck is 2.5 m long. If the truck is moving due north at 30 $ms^{- 1}$ at a place where the vertical component of the earth’s magnetic field is 90$\mu$T, the potential difference between the two ends of the axle is
A) 6.75 mV with west end positive
B) 6.75 mV with east end positive
C) 6.75 mV with north end positive
D) 6.75 mV with south end positive
Explanation
(a) While moving due north, the truck intercepts vertical component of earth’s field.
$\therefore\ \ e = Blv = \left( 90 \times 10^{- 6} \right)2.5 \times 30$
= $6.75 \times 10^{- 23}$V = 6.75 mV
According to Lenz’s law, west end of the axle will be positive.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.