Question

An electric oven is designed to work on the mains voltage of 220 V. This oven consumes 11 units of electrical energy in 5 hours. Calculate:

1. power rating of the oven
2. current drawn by the oven
3. resistance of the oven when it is red hot

Answer 1

1. Power Rating of the Oven

The oven consumes 11 units of electrical energy in 5 hours. Here, 1 unit of electrical energy = 1 kilowatt-hour (kWh).

So, total energy consumed in 5 hours: E = 11 kWh

`P = E/t`

E = 11 kWh, t = 5 hours.

`P = 11/5 = 2.2 kW`

2.2 kW

2. Current Drawn by the Oven

The power rating of the oven is P = 2.2 kW = 2200 W, and the mains voltage is V = 220 V.

`I = P/V`

Substitute the values:

`I = 2200/220 = 10A`

Thus, the current drawn by the oven is: 10 A

3. Resistance of the Oven

The resistance (R) of the oven can be calculated using Ohm's law:

`R = V/I`

`R = 220/10 = 22 Ω`

Thus, the resistance of the oven when it is red hot is: 22 Ω

Final Answers:

1. Power Rating: 2.2 kW
2. Current Drawn: 10 A
3. Resistance: 22 Ω