Power

Ashfield Direct Learning

Kirsten Lounds.

Ks4 Energy

Calculating Power.

If we know the energy transferred and time, we can calculate the power rating or energy consumed per second

To help with this you can rearrange the formula.

A simple formula triangle will help.

E

P T

Power Ratings of Domestic Appliances. All electrical appliances have a power rating This tells you how much energy is transferred by the

appliance every second.

Power rating (W)

900W

Power Rating (kW)

0.9Kw

Energy Transferred (J/s)

900J/s

The greater the power rating, the more energy is transferred.

Working Out Power Ratings Of Domestic Appliances.

A toaster transfers 108,000J of energy in the 120secs it takes to toast bread.

P=E/T P=108, 000J/120secs P=900J/s 900W or

0.9kW

Power rating (W)

900W

Power Rating (kW)

0.9kW

Energy Transferred (J/s)

900J/s