Energy transfer

Question 1

How hair dryer and a washing machine transfer electrical energy into kinetic and thermal energy and why?

Answer 1

The electric energy is transferred into kinetic energy to power the motors and suck the air through the hair dryer and the thermal energy heats the air. A washing machine needs kinetic energy to move the drum and washes the clothes and uses thermal energy to heat the water.

Question 2

What is power measured in?

Answer 2

Watts and Joules

Question 3

How many Joules is 1 watt per second?

Answer 3

1

Question 4

What is the definition of work done?

Answer 4

Whenever force is used to move an object

Question 5

What is the definition of a joule in N/m?

Answer 5

When an object is moved 1m by a force of 1N, 1J of work is done.

Question 6

What is internal energy?

Answer 6

Internal energy is the amount of energy stored in a system by the particles.

Question 7

What happens to the internal energy of a substance when you heat it up and cool it down?

Answer 7

When you heat up a substance the internal energy increases and when you cool it down the internal energy decreases.

Question 8

What happens to the amounbt of particles during changes of state?

Answer 8

Nothing, you dont lose or gain any particles

Question 9

What is the definition of a specific heat capacity of a substance?

Answer 9

The amount of energy needed to raise 1Kg of a substance’s temperature by 1 degree.

Question 10

What does latent heat mean?

Answer 10

Latent heat means the energy needed to change a substance’s state

Question 11

How can you increase the pressure of a gas that’s in a container (in terms or particles)?

Answer 11

You can increase the amount of collisions or the energy of collisions with the walls, you could do this by increasing the temperature.

Question 12

What is the link between temperature and kinetic energy in terms of particle collisions?

Answer 12

the lower the temperature, the lower the energy and the amount of collision/ lower temperature.

Question 13

What is the specific latent heat of fusion of a substance?

Answer 13

The amount of energy required to change 1Kg of substance from solid to liquid with no change in temperature.

Question 14

What is specific latent heat of vaporization?

Answer 14

The amount of energy needed to change 1Kg of a substance from a liquid to a vapour with no change in temperature.

Question 15

what energy store does a stretched string have?

Answer 15

Elastic Potential Energy

Question 16

What is extension measured in

Answer 16

meters

Question 17

What is a specific heat capacity of an object?

Answer 17

The amount of energy required to raise 1kg of substance by 1 degree celsius

Question 18

What is thermal energy?

Answer 18

The energy stored due to an object’s temperature

Question 19

Whats gravitational potential energy?

Answer 19

The energy stored in an object based on the objects height

Question 20

What energy transfers as a pendulum swings?

Answer 20

At the highest point it has the most GPE and the least KE, at the lowest point it has the most KE and the least GPE. As the pendulum moves across the air, there is friction between the pendulum and the particles in the air which causes the air and the pendulum to heat which is thermal energy, as more energy is transferred to this less will be transferred to the KE and GPE which leads it to slow down.

Question 21

What energy transfers happen during a bungee jump?

Answer 21

Before the person jumps they have GPE, once they jump the GPE is transferred into KE and thermal energy (friction) which dissipates. When the jumper reaches full extension they have only EPE and when they begin to ascend they gain more GPE and KE and lose EPE. This cycle continues until the jumper stops and has no KE and only EPE.

Question 22

What is mechanical force?

Answer 22

using force to move an object

Question 23

What is electrical work?

Answer 23

When a current transfers energy?

Question 24

What is power?

Answer 24

The rate at which energy is transferred.

Question 25

What are the jobs of step up and step down transformers and why do they have these jobs?

Answer 25

Step up transformers increase the potential difference and decrease the resistance, this decreases the energy loss in the transmission cables. The step down transformer then decreases the potential difference to about 230V before its sent into houses, this is because previously the potential difference would be too high to send into UK homes.

Question 25

What are the jobs of step up and step down transformers and why do they have these jobs?

Answer 25

Step up transformers increase the potential difference and decrease the resistance, this decreases the energy loss in the transmission cables. The step down transformer then decreases the potential difference to about 230V before its sent into houses, this is because previously the potential difference would be too high to send into UK homes.

Question 26

What is the density of a material?

Answer 26

the amount of mass packed into a certain volume, e.g a brick has a high density and something like a polystyrene block has a low density because it has a low mass packed into a certain volume

Question 27

Why do solids and liquids normally have a high density?

Answer 27

Because lots of particles are closely packed together, they normally have a higher mass for their volume.