Question

Electrical energy is transmitted over large distances at high alternating voltages. Which of the following statements is (are) correct?

1. For a given power level, there is a lower current.
2. Lower current implies less power loss.
3. Transmission lines can be made thinner.
4. It is easy to reduce the voltage at the receiving end using step-down transformers.

विकल्प

• a, b and c

• a, b and d

• b, c and d

• c and d

Answer 1

a, b and d

Explanation:

As we know that power = `I_(rms)^2R`

So to decrease power loss I_rms and R must be lower for a constant power supply. To decrease Irms, V_rms must be increased by step up transformer to get same power in step-up transformer

For a given power level, we find that 

P = E_rmsI_rms  ......(I_rms is low when E_rms is high)

Power loss = `I_(rms)^2` R = low  ......(∵ I_rms is low)

Now at the receiving end, high voltage is reduced by using step-down transformers.