Define the term ‘power loss' in a conductor of resistance r carrying a current i. in what form does this power loss appear ? show that to minimise the power loss in the transmission cables connecting the power stations to homes, it is necessary to have the connecting wires carrying current at enormous high values of voltage. (2)
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Power Loss: Power lost due to the resistance offered by a wire when current passes through it. It's appears in the form of heat energy.
Consider a device R, to which a power P is to be delivered via transmission cables having a resistance Rc.
If V is the voltage across R and I the current through it, then
P = V I --> I = P/V
The connecting wires from the power station to the device has a finite resistance Rc. The power lost in the connecting wires, which is wasted is Pc.
Pc = I² Rc
Substituting for I in the above equation,
Pc =(P/V)² Rc
i.e, Pc = P² Rc / V²
Thus, to drive a device of power P, the power wasted in the connecting wires is inversely proportional to V². To reduce Pc , these wires carry current at enormous values of V
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