NCERT Class XII Chapter
Electromagnetic Induction
Questions With Solutions

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Question : 7
Total: 17
A horizontal straight wire 10 m long extending from east to west is falling with a speed of 5.0 m s1, at right angles to the horizontal component of the earth’s magnetic field, 0.30 × 104 Wb m2.
(a) What is the instantaneous value of the emf induced in the wire?
(b) What is the direction of the emf?
(c) Which end of the wire is at the higher electrical potential?
Solution:  
The direction of earth’s magnetic field is in the direction of geographical south to geographical north

Let us take a convenient way to represent all the directions.

(a) Instantaneous emf ε = Bvl
ε = 0.3 × 104 × 5 × 10
= 15 × 104 volt = 1.5 mV
(b) Direction of emf. will be west to east.
(c) West end of the wire will be charged at higher potential.
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