A student tries to derive power in terms of potential difference and resistance as…

PHYSICS · Single correct · A Level · Physics · Electricity · Electricity

Problem

A student tries to derive power in terms of potential difference

V

and resistance

R

as follows: Step I

P = \dfrac{W}{t}

Step II

W = V I t

Step III

P = \dfrac{V I t}{t} = V I

Step IV Using

I = \dfrac{R}{V}

P = V \left(\dfrac{R}{V}\right) = V R

Which step is the first to contain an error? (a) Step II (b) Step I (c) Step IV (d) Step III