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

Answer:

0.01kWh

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  = $\frac{20}{1000}$   = 0.02kW

  Electrical energy  = 0.02kW x 0.5hr = 0.01kWh

Answer 2

$1000 \: watts = \: 1kW \\ 20 \: watts = \: \frac{20}{1000} \\

\: = 0.02kW \\

Electrical \: energy = 0.02kW x 0.5hr \\ = 0.01kWh$