Theory Worksheet 13.2

A light bulb has a power rating of 40 W. When the light bulb is switched on, it converts __________ of electrical energy into light and heat in one second.

• 40 W

• 40 kWh

• 40 J

• 40 V

What is the BEST answer to the following question:

"Fuses and circuit breakers are useful because they cut off the current..."

• before enough heat can build up to cause a fire

• to conserve energy

• so that we do not have to switch off the current by hand

• to help reduce our electricity bill

During a one-week holiday abroad, May accidentally left a 1,200 W air-conditioner on at home. The energy wasted is...

• 201,600 kWh

• 8,400 kWh

• 28,800 kWh

• 202 kWh

What is the cost of using Air-conditioner A in a month?

• $129.60

• $145.80

• $162

• $486

Choose ALL the components that make up the answer to:

"After replacing Air-conditioner A with Air-conditioner B, Marie saves $1.80 on her electricity bill each month. She formulates a hypothesis that this is because the power rating of her new air-conditioner is lower.

Marie’s hypothesis may not be correct. Explain how she can test her hypothesis."

• She should use Air-conditioner B for the same number of hours as she used for Air-conditioner A every night.

• She should use Air-conditioner B for a different number of hours than what she used for Air-conditioner A every night.

• She should use Air-conditioner B for a varying number of hours as what she used for Air-conditioner A every night.

• She should also keep her daily usage of other electrical appliances the same.

• She should also vary her daily usage of other electrical appliances the same.

What safety rules are being broken in this image? Choose all that apply.

• He is cleaning or repair an electrical appliance with the plug connected to the socket.

• He is trying to fix the appliance without calling the electrician to repair the damaged appliance/electrical cables.

• He is sticking something into an electrical appliance with the plug connected to the socket.

The earth wire diverts current in order to prevent _________, which would be caused by a large current flowing in the _________.

• electrocution, body

• electrocution, wires

• electrical fire, body

• electrical fire, wires

The circuit breaker cuts off current in order to prevent _________, which would be caused by a large current flowing in the _________.

• electrocution, body

• electrocution, wires

• electrical fire, body

• electrical fire, wires

A fuse...

• contains a long, thin wire that can melt

• contains a short, thin wire that can melt

• contains a long, thick wire that can melt

• contains a short, thick wire that can melt

A circuit breaker...

• is a switch-like lever that can switch a circuit between high resistance and low resistance

• is a switch-like lever that can turn off or "trip" a circuit permanently

• is a switch-like lever that can turn off or "trip" a circuit temporarily

• is a switch-like lever that can switch a circuit between series and parallel