Q. A horizontal straight wire $10\ m$ long extending from east to west falling with a speed of $5.0\ m/s$, at right angles to the horizontal component of the earth’s magnetic field of strength $0.30 \times 10^{- 4}Wb/m^{2}$. The instantaneous value of the induced potential gradient in the wire, from west to east is
A) $+ 1.5 \times 10^{- 3}V/m$
B) $- 1.5 \times 10^{- 3}V/m$
C) $+ 1.5 \times 10^{- 4}V/m$
D) $- 1.5 \times 10^{- 4}V/m$
Explanation
(a) Number of lines cut per second $= Blv$
$= 10 \times 5 \times 0.30 \times 10^{- 4}$
$\therefore\varepsilon_{induced} = - 1.5 \times 10^{- 3}V/m$
$\therefore$ From west to east, $\varepsilon = + 1.5 \times 10^{- 3}V/m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.