Question

A rectangular coil having dimensions 10 cm × 5 cm has 100 turns. It is moving at right angles to a field of 5 Tesla at angular speed of 314 rad/sec. The emf at instant when flux passing the coils is half the maximum value is

• A. 785 V
• B. $\frac { 785 } { 2 } V$
• C. $\frac { 785 \sqrt { 3 } } { 2 } V$
• D. 0

Answer 1

Answer: (C)

$\frac { 785 \sqrt { 3 } } { 2 } V$

Answer 2

$\phi = \phi _ { 0 } \cos \theta$ $\Rightarrow \frac { \phi _ { 0 } } { 2 } = \phi _ { 0 } \cos \theta ; \quad \theta = 60 ^ { \circ }$

∴ $e = e _ { 0 } \sin \theta$

$\Rightarrow e _ { 0 } = \omega N B A = 314 \times 100 \times 5 \times 50 \times 10 ^ { - 4 } = 785 \mathrm {~V}$⇒

e = 785 sin 60^o $= \frac { 785 \sqrt { 3 } } { 2 } \mathrm {~V}$