Power of Electrical Appliances

Question 1

Moving charge transfers energy. But why?

Answer 1

charge does work against the resistance of the circuit

Question 2

Electrical appliances are designed to …

example of kettle and hand held fan

Answer 2

Transfer energy

Kettle transfers energy electrically from main a.c. supply to thermal energy store of the heating element inside the kettle

Energy is transferred electrically from the battery of a HHF to the kinetic energy store of the fans motor

No appliance transfers all energy completely usefully. Higher current = the more energy is transferred to the thermal energy store of the components

Question 3

E (J) = P (W) x T (s)

Answer 3

Power is energy transferred per second so more energy transferred in given time = higher power

Question 4

Appliances are often given a power rating. What is a power rating and what does it tell you?

Answer 4

They’rd labelled with a maximum safe power that they can operate at. (Max operating power)
The power rating tells you the maximum amount of energy transferred between stores per second when appliance is in use

Question 5

How would a power rating help customers ?

Answer 5

Help them to choose between models. The lower the power rating, the less electricity an appliance uses in given time = cheaper to run

But higher power doesn’t mean it transfers more energy usefully. An appliance can be more powerful than another, but less efficienct meaning it might still transfer same amount of energy to useful store.