Question

An electric lamp is marked 100 W, 220 V. It is used for 5 hours daily. Calculate (i) its resistance while glowing (ii) energy consumed in kWh per day

Answer 1

. An electric lamp is marked 100 W, 220 V. It is used for 5 hour daily. Calculate (i)its resistance while glowing (ii)energy consumed in kWh per day. 1) R = (E^2/P), not E/P, which is nothing. (E is for volts). But I doubt you are meant to use that formula. Find current. I = (P/E) = 100/220, = 0.45455A. Resistance R = (E/I) = 220/0.4545, = 484 ohms. 2) (100W x 24 hrs) = 2,400 Watts in 24 hrs. Divide by 1,000 = 2.4kWh. (2,400 W. referenced to 1 hr).