Power and Efficiency

Which of these is an electrical appliance?

• kettle

• teapot

• spoon

• ladle

Power is ..

• the amount of internal energy in a system

• the amount of energy transferred per second

• the transfer of energy by collision of particles

• the transfer of energy by convection

How much energy appliances will transfer over time is called their

• power rating

• energy rating

• convection current

• time warp

What is the unit of energy?

• kW

• seconds

• Watts

• Joules

What is the unit of power?

• Watts

• energy

• Joules

• seconds

Energy output divided by energy input is called the

• efficiency

• power

• internal energy

• temperature

What is the efficiency when 120 J is supplied to a toaster and 60 J of heat is created?

• 0.5

• 5

• 7.2

• 2

What is the efficiency when 800 J is supplied to an electrical heater and 200 J of waste energy is created?

• 0.75

• 0.16

• 7.2

• 2

Waht is the power rating of an electrical shower transferring 10,000 J/s in kW?

• 10 kW

• 1 kW

• 100 kW

• 1000 kW

An electric kettle has a power rating of 3 kW. How much energy does it transfer each second

• 3000 J

• 3 J

• 30 J

• 30 kJ