# NCERT Physics Class 12 Exemplar Ch 7 Alternating Current Part 5

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**28 **1MW power is to be delivered from a power station to a town 10 km away. One uses a pair of Cu wires of radius cm for this purpose. Calculate the fraction of ohmic losses to power transmitted if

(i) Power is transmitted at Comment on the feasibility of doing this.

(ii) A step-up transformer is used to boost the voltage to, power transmitted, and then a step-down transformer is used to bring voltage to 220 V.

Resistance of Cu wires, R

I at

Power loss

This method cannot be used for transmission

Fraction of power loss

**29 **Consider the *LCR *circuit shown in Figure. Find the net current *i *and the phase of *i*. Show that. Find the impedence Z for this circuit.

**Ans:**

andare out of phase. Let us assume

Now A

**Therefore, **