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13

13. a. Derive an expression for maximum induced emf produced by an AC generator.

b. Draw a graph to show the variation of induced emf with time for one complete cycle of the armature coil. c. Draw graphical variation of magnetic flux linked with the armature coil with time for one complete cycle of the armature coil.
**OR**

a. Derive an expression for average power consumed by a series LCR circuit from AC source of voltage ${V}_{\left(t\right)}={V}_{\left(0\right)}Sin\omega t$

b. A bulb is connected to series combination of inductor and capacitor along with an AC source. Explain the change in brightness of the bulb as frequency of the source is increased from zero to infinity.

**OR**

$letthenoofturninthecoilbeNandtheareaofthecoilbeA\phantom{\rule{0ex}{0ex}}letitberotateattheangularspeed\omega .\phantom{\rule{0ex}{0ex}}fluxlinkingvariesasthecoilrotateswiththemagneticfield.\phantom{\rule{0ex}{0ex}}\varphi =NBA\mathrm{cos}\omega t\phantom{\rule{0ex}{0ex}}e=\frac{-d\varphi}{dt}=NBA\omega \mathrm{sin}\omega tthisistheexpressionfortheinducedEmf.\phantom{\rule{0ex}{0ex}}$

Regards

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