Question

An electric bulb is rated as 240V, 40W. Calculate ---(i) the electric current through it(ii) the resistance of its filament when it is glowing(iii) Energy consumed by it in kWh when it is used for 5 hours

Answer 1

Potential difference ( v ) :- 240 v

Power ( P ) :- 40W

i ) Let electric current through it be I

P = VI

40 = 240 × I

40/240 = I

1/6 = I

0.16 amp = I

Current = 0.16 amp



ii ) V = IR

240 = 0.16 R

240/0.16 = R

1500 = R

150 Ohms = R


iii ) E = Pt

E = 40/1000 × 5

E = 0.04 × 5

E = 0.2 Kwh