Question

Calculate the number of units of electricity used if a bulb of 100 W is kept on for 5 hours.

(a) 1 unit

(b) 0.1 unit

(c) 5 unit

(d) 0.5 unit

The question was asked in an internship interview.

This key question is from Current Electricity in chapter Current Electricity of Physics – Class 12

Answer 1

Correct answer is (d) 0.5 unit

The best I can explain: The number of units of electricity consumed is

n = \(\frac {(total \, wattage \, \times \, time \, in \, hour)}{1000}\)

Total wattage = 100 W      Time in hour = 5 hours

Therefore,     n = \(\frac {100 \times 5}{1000}\)

= 0.5 units

So, the number of units of electricity consumed is 0.5 units.