Question

Calculate the number of units of electricity used if a bulb of 18 W is kept on for 9 hours.

Answer 1

Given Data:

Power of the bulb (P) = 18 W = `18/1000` kW = 0.018 kW

Time duration (t) = 9 hours

Formula:

The commercial unit of electricity consumed is measured in Kilowatt-hours (kWh), where 1 kWh = 1 unit.

Electrical Energy (E) = Power (P in kW) × Time (t in hours)

= 0.018 kW × 9 hours

= 0.162 kWh

Since 1 kWh = 1 electrical unit

Number of units = 0.162 units

The total number of units of electricity used by the bulb is 0.162 units.