Chap 6 Calculations Qs

Question 1

The electric jug is rated 2.2 kW, 240 V. Calculate the current that flows through it

Answer 1

Use Equation P= VI
I = P/V
= 2.2kW/ 240 V
= 2200 W/ 240 V
= 9.17 A

Question 2

A 2kW electric kettle takes 10mins to boil water. Calculate the cost of electrical energy used to boil the water if the rate per unit is 21 sen

Answer 2

Using formula: Power (kW) x Time (h)
= 2 kW x 10/60 h
= 1/3 kWh
= 1/3 unit
Cost: 1/3 unit x 21sen
= 7 sen

Question 3

Electric heater is rated 230 V , 10 A. Calculate the power of the electric heater in kW

Answer 3

Using formula: Power = voltage V x electric current A
230 V x 10A
= 2300 W
= 2300/1000 kW
= 2.3 kW