P1+2 Energy

Question 1

What are the energy pathways?

Answer 1

Heating, radiation, mechanical, electrical

Question 2

What are the energy stores?

Answer 2

Chemical, thermal, kinetic, elastic, gravitational, electrostatic, nuclear

Question 3

What is conservation of energy?

Answer 3

Energy can’t be created or destroyed, this applies to all energy changes.

Question 4

What is a closed system?

Answer 4

A system in which no energy transfers take place out of or into the energy stores of the system.

Question 5

Work done equation

Answer 5

work done, W(j) = force applied, F(n) x distance travelled, d(m)

Question 6

What does energy transferred equal?

Answer 6

Work done.

Question 7

Gravitational potential energy equation

Answer 7

GPE(j) = mass, m(kg) x gravitational field strength, g(N/Kg) x height, h(m)

Question 8

Kinetic energy equation

Answer 8

1/2 x mass, m(kg) x speed^2, v^2 (m/s^2)

Question 9

Elastic potential energy equation

Answer 9

1/2 x spring constant, K(N/m) x extension^2, e^2(m^2)

Question 10

What is Useful energy?

Answer 10

Energy transferred to where it is wanted in the way it is wanted.

Question 11

What is Wasted energy?

Answer 11

Energy that is not usefully transferred.

Question 12

What happens to energy as it dissipates (spreads out)

Answer 12

It becomes less and less useful

Question 13

Equation for efficiency

Answer 13

efficiency=useful output energy transferred by the device(j)/total input energy supplied to the device(j)

Question 14

Equation for power

Answer 14

power, p(w) = energy transferred to appliance, e(j)/time taken for energy to be transferred, t(s)

Question 15

Equation for specific heat capacity

Answer 15

Change in energy, ∆E(j) = mass, m(kg) x specific heat capacity, c(j/kg) x temperature change, ∆θ(°C)

Question 16

What does the specific heat capacity of a substance mean?

Answer 16

The energy needed to change 1Kg of a substance by 1°C

Question 17

What are examples of electrical appliances and why are they used?

Answer 17

They could be heating, lighting and producing sound. They can transfer energy quickly and efficiently so they do not waste energy.

Question 18

What actually is power?

Answer 18

The energy you supply per second is the power.

Question 19

How to calculate power wasted?

Answer 19

power wasted = total power in - useful power out

Question 20

What are the best conductors of energy?

Answer 20

Metals

Question 21

What is thermal conductivity?

Answer 21

Thermal conductivity is the rate at which energy is transferred through something by conduction.

Question 22

What does insulation do to energy transfer?

Answer 22

The thicker the layer of insulating material, the lower the rate of energy transferring through.

Question 23

What is infrared radiation?

Answer 23

It is part of the electromagnetic spectrum and is given out by the sun. All objects emit and absorb infrared radiation. It also increases the amount emitted with the heat.

Question 24

What is black body radiation?

Answer 24

It is the radiation emitted by a perfect black body. It absorbs all the radiation incident on it.

Question 25

What happens to infrared radiation if the body has a constant temperature?

Answer 25

It emits the same amount at the same rate as it absorbs it.

Question 26

What are some factors affecting the temperature of the earth?

Answer 26

The rate that light and infrared radiation are reflected back into space or absorbed by the earths atmosphere or surface and emitted from the earths surface and atmosphere into space.

Question 27

How can you reduce the rate of energy transfer from a home?

Answer 27

You can use loft insulation(fibreglass), you can use cavity wall insulation reducing the amount of energy transfer by conduction, you can use aluminium foil between a radiator and a wall to reflect radiation away from the wall, you can use double glazed windows and you can use external walls with thicker bricks and lower thermal conductivity

Question 28

How do solar panels work?

Answer 28

They absorb infrared radiation from the sun and are used to generate electricity directly or to heat water directly.