All electrical devices in the home should have labels on them that show the power rating of the device.
The label will include:
2,000 W means that the kettle transfers 2,000 J of energy per second from one store to another.
Other electrcial transfers in the home may include:
|Appliance||Power in W||Power in kW|
|Hot water heater||3,000||3|
How much energy is transferred each second when a 50 W lamp is turned on?
50 W is equivalent to 50 joules per second so a 50 W lamp transfers 50 joules every second.
How much energy is transferred when a 50 W light bulb is turned on for 10 minutes?
= 50 × (10 × 60)
= 50 × (600)
= 30,000 J
When a charge moves through a potential difference, electrical work is done and energy transferred. The energy transferred can be calculated using the equation:
energy = charge flow × potential difference
This is when:
One volt is the potential difference when one coulomb of charge transfers one joule of energy.
What is the potential difference between two points if 2 C of charge shifts 4 J?
= 2 V
How much energy is transferred when 3 C of charge moves through a potential difference of 6 V?
= 6 × 3
= 18 J