Energy stores and transfers

Question 1

Name the eight energy stores.

Answer 1

• Kinetic
• Gravitational Potential
• Elastic potential
• Thermal
• Chemical
• Nuclear
• Magnetic
• Electrostatic

Question 2

Name the four ways in which energy can be transferred.

Answer 2

• Heating (e.g burning)
• Waves (e.g radio)
• Electric current (e.g circuits)
• Mechanically (e.g forces)

Question 3

What is a system?

Answer 3

An object or group of objects

Question 4

What is a closed system?

Answer 4

A system where no energy can be transferred to or from the surroundings.
The total energy of the system stays the same.

Question 5

What is the unit for energy?

Answer 5

Joules (J)

Question 6

What is work done?

Answer 6

Energy transferred when force moves an object.
J = N x M

Question 7

What is one joule of work?

Answer 7

The work done when 1N causes an object to move by 1m in the direction of the force.
e.g. 1N x 1m = 1J

Question 8

Describe the energy transfer when a moving car slows down.

Answer 8

• Energy is transferred mechanically from the kinetic store of the car to the thermal store of its brakes.
• Some energy is dissipated to the thermal store of the surroundings.

Question 9

Describe the energy transfer when a ball is fired using an elastic band.

Answer 9

• Energy is transferred mechanically from the elastic potential store of the elastic band to the kinetic store of the band.
• Some energy is dissipated to the thermal store of the surroundings.

Question 10

Describe the energy transfer when a electric kettle is used to heat water.

Answer 10

• The electric current in a kettle transfers energy to the heating element’s thermal store.
• Energy is then transferred by heating from the heating element’s thermal store to the thermal store of the water.

Question 11

Describe the energy transfer when a falling apple hits the floor.

Answer 11

• Energy is transferred from the kinetic store of the apple and dissipated to the thermal store of the surroundings by sound waves.

Question 12

Name the unit that represents one joule transferred per second.

Answer 12

Watt (W)

Question 13

What does a material’s thermal conductivity tell you?

Answer 13

How well it conducts heat.

Question 14

Which materials have low thermal conductivity?

Answer 14

Thermal insulators.

Question 15

Give three factors that determine the rate of thermal energy transfer through a material.

Answer 15

• Thermal conductivity of the material.
• Temperature difference,
• Thickness of the material.

Question 16

What factors affect the rate of heat loss from a building?

Answer 16

• Thickness of walls and roof.
• Thermal conductivity of the walls and roof.
• The temperature difference between the two sides of the walls and roof.