4.2.4.2 Energy Transfers in Everyday Appliances

Question 1

What are every day electrical appliances designed to do?

Answer 1

every day electrical appliances are designed to bring about energy transfers

Question 2

What does the amount of energy an appliance transfers depend on?

Answer 2

• how long the appliance is switched on for
• power of the appliance

Question 3

How do different domestic appliance transfer energy?

Answer 3

• different domestic appliance transfer energy from batteries or ac mains to the kinetic energy store of electric motors or the thermal energy store of heating devices
• some appliances transfer electrical energy to its thermal and kinetic energy stores

Question 4

When is work done in a circuit?

Answer 4

work is done when charge flows through a circuit

Question 5

How is the power of a circuit device related to the potential difference and current across it and the energy transferred over a given time?

Answer 5

• If either p.d. or current increases, the power increases
  
  • energy is transferred at a faster rate and more energy is transferred at once
• Electrical energy use equals the power of the appliance multiplied by the amount of time the appliance is used

Question 6

Calculating the amount of energy transferred by electrical work:

Answer 6

Question 7

Relationship between power ratings for domestic electrical appliances and the changes in stored energy when they are in use:

Answer 7

• 1W is equivalent to 1 J of energy transferred per second
• appliances used to generate thermal energy usually have much higher rating than appliances used to generate kinetic energy