Embibe Experts Solutions for Chapter: Alternating Current, Exercise 1: cbse-2018

 In a series LCR circuit connected across an ac source of variable frequency, obtain the expression for its impedance and draw a plot showing its variation with frequency of the ac source

 What is the phase difference between the voltages across inductor and the capacitor at resonance in the LCR circuit ?

When an inductor is connected to $200 V$dc voltage, a current of $1 A$ flows through it. When the same inductor is connected to a $200 V$, $50 Hz$ ac source, only $0.5 A$ current flows. Explain, why ? Also, calculate the self inductance of the inductor. 

Draw the diagram of a device which is used to decrease high ac voltage into a low ac voltage and state its working principle. Write four sources of energy loss in this device.

A small town with a demand of $1200 KW$ of electric power of $220 V$ is situated $20 Km$ away from an electric plant generating power at $440 V$. The resistance of the two wireline carrying power is $0.5 \Omega per km.$ The town gets power from the line through a $4000-220 V$step-down transformer at a sub-station in the town. Estimate the line power loss in the form of heat.

Laminated iron sheets are used to minimize _____ currents in the core of a transformer.

With the help of a labelled diagram, explain the working of a step-up transformer.

Give reasons to explain the following:

(i) The core of the transformer is laminated.

(ii) Thick copper wire is used in windings.