Energy transfers

Question 1

What is the Principle of Conservation of Energy?

Answer 1

Energy can neither be created not destroyed: it can only be transformed from one state to another

Question 3

What is conduction?

Answer 3

The process where vibrating particles pass on their extra kinetic energy (or heat) to neighbouring particles

Question 4

How would you calculate efficiency?

Answer 4

Efficiency = (energy output ÷ total energy output) x 100

Question 5

Why is conduction most effective in solids?

Answer 5

Because the particles are close together and strongly bound to each other

Question 6

Why are metals good conductors of heat?

Answer 6

They contain free electrons that assist in transferring kinetic energy

Question 7

What is convection?

Answer 7

When the more energetic particles move from the hotter region to the cooler region and take their heat energy with them

Question 8

What is radiation?

Answer 8

The emission of infrared waves (The hotter an object the more radiation)

Question 9

What are the best/worst emitters/absorbers of radiation?

Answer 9

Best- matt black Worst- shiny silver surfaces

Question 10

Role of convection in weather? (And use)

Answer 10

Thermals are warm current of air

gilder pilots and birds use them to rise higher

Question 11

How to reduce conduction in housing?

Answer 11

Cavity wall insulation Double glazing Loft insulation

Question 12

How to reduce convection in housing?

Answer 12

Loft insulation Draught excluders

Question 13

How to reduce radiation in housing?

Answer 13

Reflective foil behind radiators

Question 14

Why does trapped air reduce heat loss?

Answer 14

Because the air cannot circulate and is a very poor conductor

Question 15

If someone is dangerously cold how would you warm them up?

Answer 15

Wrap them in a highly reflective ‘space’ blanket They reflect thermal radiation and prevent convection

Question 16

How would you calculate the work done?

Answer 16

Work done (J) = force (N) x distance moved (m) fd

Question 17

When is work done?

Answer 17

When a force makes something move in the direction of the force

Question 18

How do you calculate the energy transferred?

Answer 18

It is equal to the work done

Question 19

How would you calculate the gravitational energy?

Answer 19

GPE (J) = Mass (kg) x g x height (m) (G is gravitational field strength) mgh

Question 20

How would you calculate the kinetic energy?

Answer 20

Kinetic energy (J) = 1/2 x mass (kg) x speed (m/s) 1/2mv²

Question 21

What’s the relationship between KE and GPE

Answer 21

They are equal in some situations mgh = 1/2mv²

Question 22

How would you calculate the power?

Answer 22

Power (W) = work done (J) ÷ time taken (s)

Question 23

Types of energy we need to know:

Answer 23

Thermal (heat) energy, light, electrical, sound, kinetic (movement) energy, chemical energy, nuclear energy, gravitational potential energy and elastic potential energy.

Question 24

What does ‘wasted’ or ‘lost’ energy actually mean?

Answer 24

‘Wasted’ energy can mean ‘lost’ from the system or converted into unwanted forms. Like the noise produced by a motor when what we want is kinetic energy.

Question 25

Describe the energy transfers taking place when you strike a match.

Answer 25

You provide some KE as you drag the match head across the striking paper and this is converted into thermal energy; this heat starts the chemical reaction that concerts the chemical energy into thermal energy and light (and a tiny bit of sound).

Question 26

What is power?

Answer 26

Power is the rate of transfer of energy or the rate of doing work