Question

Define Power and state its SI unit. (b) A torch bulb is rated 5 V and 500 mA. Calculate its (i) Power (ii Resistances (iii) Energy consumed when it is lighted for 2 and a half-hour ( in KWH)

Answer 1

Answer:

(1) P = 2.5 watt

(2) R = 10 ohms

(3) Energy consumed = 36 k J or 0.01 kw H

Explanation:

(1) Power P = V x I = 5 V x 0.5 A = 2.5 watt

(2) Resistance R = V / I = 5 / 0.5 = 10 Ohms

(3) ENERGY CONSUMED = V x I x t = 5 x 0.5 x 4 x 3600 = 36000 J = 36 k J.

                                                     OR

(3) ENERGY CONSUMED = P x t = (2.5 / 1000) kw x 4 h = 0.01 kw H