Question

How much energy, in kWh, is used if a hair dryer with a power of 20 watts was used for

0.5 hours? (Remember to convert to kW first!!!!)

Answer 1

`1000 \: watts = \: 1kW \\ 20 \: watts = \: (20)/(1000) \\ </p><p> \: = 0.02kW \\ </p><p> Electrical \: energy = 0.02kW x 0.5hr \\ = 0.01kWh`

Answer 2

0.01kWh

Step-by-step explanation:

Given parameters:

Power = 20watts

Time = 0.5hrs

Unknown:

Energy of other dryer = ?

Solution:

The electrical energy of the dryer can be calculated using the expression below;

Electrical energy = IVt

P = IV

I is the current

V is the voltage

t is the time

P is the power

Convert 20watts to kilowatts;

1000watts = 1kW

20watts =
`(20)/(1000)` = 0.02kW

Electrical energy = 0.02kW x 0.5hr = 0.01kWh