. 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).