Q. A horizontal straight wire 20 m long extending from east to west is falling with a speed of 5.0${ms}^{- 1},$at right angles to the horizontal component of the earth’s magnetic field $0.030 \times 10^{- 4}{Wbm}^{- 2}.the\ instantaneous\ $value of the emf induced in the wire will be
A) 6.0 mV
B) 3 mV
C) 4.5 mV
D) 1.5 mV
Explanation
(b) Induced emf
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ e = B_{H}lv$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = 0.30 \times 10^{- 4} \times 20 \times 5.0 = 3mV$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.