A long solenoid having $$200$$ turns per centimeter carries a current of $$1.5$$ A. At the center of the solenoid is placed a coil of $$100$$ turns of $$cross-sectional$$ area $$3.14$$ x $$10-4$$ $$m2$$ having its axis parallel to the field produced by the solenoid. When the direction of current in the solenoid is reversed within $$0.05$$ s, the induced emf in the coil is

Question

Infinity Learn · Accepted Answer

$$B=$$μ$$0ni=4$$π×$$10$$−$$7$$×$$200$$×$$102$$×$$1.5=3.8$$×$$10$$−$$2T$$ϕ$$=BA=3.8$$×$$10$$−$$2$$×$$3.14$$×$$10$$−$$4=1.2$$×$$10$$−$$5WbWhen$$ the current in the solenoid is reversed, the change in magnetic flux,dϕ$$=2$$×$$1.2$$×$$10$$−$$5=2.4$$×$$10$$−$$5Wb$$∴  Induced e.m.f. ε$$=Nd$$ϕ$$dt=100$$×$$2.4$$×$$10$$−$$50.05=0.048V$$

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