Question

(a) Define electric power. Express it in terms of potential difference V and resistance R. 

(b) An electrical fuse is rated at 2 A. What is meant by this statement? 

(c) An electric iron of 1 kW is operated at 220 V. Find which of the following fuses that respectively rated at 1 A,3 A and 5 A can be used in it.

Answer 1

(a) Electric power: It is the rate of doing work by an energy source or the rate at which the electrical energy is dissipated or consumed per unit time in the electric circuit is called electric power.

So, Power P = Work done (w)/Time (t)

= Electrical energy dissipated/Time (t)

= Vl = V²/R

(b) It means: the maximum current will flow through it is only 2 A. Fuse wire will melt if the current exceeds 2 A value through it.

(c) Given: p = 1 k W = 1000 W, V = 220 V

Current drawn, I = p/V = 1000/220 = 50/11 = 4.54 A

To run electric iron of 1 kW, rated fuse of 5 A should be used.