An adjustable resistor whose value can be varied between and is connected to a…

PHYSICS · Subjective · CBSE · Physics · Current Electricity · Current Electricity

Problem

An adjustable resistor whose value can be varied between

20\,\Omega

and

80\,\Omega

is connected to a regulated d.c. supply. The circuit is required to deliver a constant power of

200\,\text{W}

to the resistor for any chosen resistance within this range. (i) Derive an expression for the supply voltage

V

in terms of the resistance

R

under the constant-power condition. (ii) Calculate the supply voltage needed when (1)

R=20\,\Omega

and (2)

R=80\,\Omega

. (iii) For

R=20\,\Omega

and

R=80\,\Omega

, determine the corresponding current in the circuit and comment on the trend you observe.