Section 4-Energy Resources and Energy Transfer P1

Question 1

What are the 8 different types of energy stores that energy can be transferred between?

Answer 1

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

Question 2

Define a kinetic energy store:

Answer 2

Anything moving has energy in its kinetic energy store

Question 3

Define a thermal energy store:

Answer 3

Any object - the hotter it is the more energy it has in this store

Question 4

Define a chemical energy store:

Answer 4

Anything that can release energy by a chemical reaction (e.g. food, fuel)

Question 5

Define a gravitational potential energy store:

Answer 5

Anything in a gravitational field (i.e. anything which fall)

Question 6

Define a elastic potential energy store:

Answer 6

Anything stretched, like springs and rubber bands

Question 7

Define a electrostatic energy store:

Answer 7

E.g. two charges that attract or repel each other

Question 8

Define a magnetic energy store:

Answer 8

E.g. two magnets that attract or repel each other

Question 9

Define a nuclear energy store:

Answer 9

Atomic nuclei release energy from this store in nuclear reactions

Question 10

What four main ways can energy be transferred between stores?

Answer 10

Mechanically
Electrically
By heating
By radiation

Question 11

How can energy be transferred between stores mechanically?

Answer 11

An object moving due to a force acting on it (e.g. pushing, pulling, stretching or squashing)

Question 12

How can energy be transferred between stores electrically?

Answer 12

A charge moving through a potential difference (e.g. charges moving round a circuit)

Question 13

How can energy be transferred between stores by heating?

Answer 13

Energy transferred from a hotter object to a colder object (e.g. heating a pan of water on a hob)

Question 14

How can energy be transferred between stores by radiation?

Answer 14

Energy transferred (e.g. by light/sound waves, e.g. energy from the sun reaching earth as light)

Question 15

What’s the principle of conservation of energy?

Answer 15

Energy can be stored, transferred between stores, and dissipated(spread out) - but it can never be created or destroyed. The total energy of a closed system(a system that can be treated on its own without any matter being exchanged with the surroundings) has no net change.

Question 16

When is energy useful?

Answer 16

Energy is only useful when it’s transferred from one store to a useful store.

Question 17

What does the law of conservation of energy also mean that?

Answer 17

Total energy input = useful energy output + wasted energy

Question 18

Most energy transfers involve some wasted energy often to thermal energy stores. What is it called when less energy is wasted?

Answer 18

More efficient

Question 19

What’s the equation to calculate efficiency of an energy transfer?

Answer 19

useful energy output
Efficiency = ————————————x 100(%)
total energy output/input

Question 20

What happens to wasted energy?

Answer 20

• We generally can’t do anything with wasted energy
• Wasted energy is an output that is transferred to less useful stores(normally thermal, light, sound) this energy is transferred away from the source and dissipates

Question 21

Describe the energy transfer of a ball rolling up a slope:

Answer 21

Energy is transferred mechanically from kinetic energy to gravitational potential and thermal energy(due to friction the thermal energy is wasted)

Question 22

Describe the energy transfer of a bat hitting a ball:

Answer 22

Some useful energy is transferred mechanically from the kinetic store of the bat to the kinetic store of the ball. The rest of the energy is wasted transferred from kinetic mechanically to thermal and sound.

Question 23

Describe the energy transfer of an electric kettle boiling water:

Answer 23

Energy is transferred electrically from the thermal store of the kettles heating element to the thermal in the water. Some thermal energy is wasted to the surroundings.

Question 24

Describe the energy transfer of a battery-powered toy car:

Answer 24

Energy is usefully transferred electrically from the chemical energy store of the battery to the kinetic energy store of the car and carried away by light from the headlights. Wasted energy are also from chemical to thermal and sound

Question 25

Describe the energy transfer of a Bunsen burner and a beaker:

Answer 25

Energy is usefully transferred by heating from the chemical energy store of gas to the thermal energy stores of the beaker and water. Energy is also wastefully transferred by heating as light.

Question 26

What’s a Sankey diagram?

Answer 26

Sankey(energy transformation) diagrams are a way of representing how much of the input energy is being usefully employed and how much is being wasted.
-The thicker the arrow the more energy it represents

Question 27

What are the three different ways energy can be transferred by heating?

Answer 27

Radiation
Conduction
Convection

Question 28

Define thermal radiation:

Answer 28

Thermal radiation is the transfer of energy by heating by infrared electromagnetic waves.

Question 29

Define conduction:

Answer 29

Conduction is the main form of energy transfer by heating particles in solids

Question 30

Define convection:

Answer 30

Conduction is the main form of energy transfer by heating particles in liquids and gases

Question 31

What state(s) of matter can thermal radiation be absorbed or emitted in?

Answer 31

Solid, Liquid and Gas

Any object can absorb or emit thermal radiation whether or not conduction or convection are also taking place

Question 32

What’s the correlation between temperature difference and the rate by which energy is transferred?

Answer 32

The bigger the temperature difference, the faster energy is transferred.

Question 33

What’s thermal radiation?

Answer 33

Thermal radiation/infrared radiation is just electromagnetic waves with a certain range of frequencies.

• all objects are continually emitting and absorbing infrared radiation
• an object that is hotter than its surroundings emits more radiation than it absorbs, an object that is cooler than its surroundings emits less radiation than it absorbs

Question 34

Define thermal conduction:

Answer 34

Thermal conduction is the process where vibrating particles transfer energy from their kinetic energy store to the kinetic energy stores of neighbouring particles.

Question 35

What’s conduction?

Answer 35

In a solid particles are close together so when one vibrates it collides with other nearby particles. This process continues throughout the solid and gradually some of the energy is passed through the solid causing a rise in temperature.

Question 36

Describe an experiment to demonstrate conduction:

Answer 36

• attach beads at regular intervals to a long metal bar using wax
• hold the metal bar in a clamp stand, use a Bunsen burner to heat the side of the bar with no beads attached from the very end
• as time goes on energy is transferred along the bar by conduction
• the wax will gradually melt and the beads will fall as the temperature increases (this illustrates conduction)

Question 37

Define convection of heat:

Answer 37

Convection occurs when the more energetic particles move from the hotter region to the cooler region - and transfer energy as they do.

Question 38

What are convection currents about?

Answer 38

Convection currents are all about changes in density.

Question 39

Explain convection in an immersion heater:

Answer 39

• energy is transferred from the heater coils to the water by conduction
• the particles near the coils moved around faster so there’s more distance between them(expands)and becomes less dense
• reduction in density means the hotter water rises above(displaces) the cooler denser water making the cooler water sink toward the coils
• the cold water is then heated by the coils and rises and the cycle continues you’ll end up with convection currents circulating the energy throughout the water

Question 40

When is convection most efficient?

Answer 40

In roundish or squarish containers because they allow convection currents to work best.

Question 41

What water in the immersion heated wont heat up?

Answer 41

The water below the heater coils because convection happens above and there’s almost no conduction

Question 42

Describe a practical to see convection current:

Answer 42

• place purple potassium permanganate crystals in a beaker of cold water(on one side of the beaker)
• heat the beaker gently with a Bunsen burner underneath the crystals
• as the temperature of the water increases around the crystals they begin to dissolve forming a bright purple solution
• this purple solution is carried through the water by convection

Question 43

How can you reduce the rate of thermal conductivity? And what’s an example of a strategy

Answer 43

Some materials have low thermal conductivity
An example of a material like this is insulation(air can’t move so energy has to conduct very slowly through the pockets of air

Question 44

How can you reduce the rate of convection? And what’s an example of a strategy

Answer 44

To reduce convection you need to stop the fluid moving and prevent convection currents from flowing
Insulation is an example of a poor material for convection

Question 45

How can you reduce the rate of thermal radiation? And what’s an example of a strategy

Answer 45

To reduce the amount of energy transfers away from an object by thermal radiation, the object should be designed with a surface that is a poor emitter(e.g. white and shiny)

Question 46

What is a Leslie cube?

Answer 46

It’s a hollow, watertight metal cube whose four vertical faces have different surfaces.(e.g. black paint, white paint, shiny metal, dull metal)

Question 47

Describe how you can investigate emissions of thermal radiation with a Leslie cube?

Answer 47

• place a empty Leslie cube on a heat proof mat
• boil water in a kettle and fill the cube with boiling water
• wait for the cube to warm up then hold a thermometer against each of the faces you should find all the faces have the same temperature
• hold an infrared detector a set distance away and record the amount of IR radiation
• repeat this for each of the faces making sure the detector is the same distance away and compare your results

Question 48

Why is work done the same as energy transferred?

Answer 48

When a force moves an object through a distance, work is done on the object and energy is transferred.

• to make something move some sort of force needs to act on it
• the force does ‘work’ to move the object and energy is transferred
• whether energy is transferred usefully or not work is still done and therefore energy transferred=work done

Question 49

When is friction cause and what does it lead to?

Answer 49

Friction is caused when you push something along a rough surface
Energy is transferred to kinetic and wasted thermal energy

Question 50

What’s the equation linking Force, Work done and Distance moved? And what are the units?

Answer 50

Work done(J) = Force(N) x Distance moved(m)

Question 51

Define power:

Answer 51

Power is the rate at which energy is transferred.

Question 52

What’s the equation linking Time taken, Work done and Power? And what are the units?

Answer 52

Work done(J)
Power(W) = ————————
                  Time taken(s)

Question 53

1 Watt = ?

Answer 53

1J of energy transferred per second (J/s)

Question 54

What links movement and an objects kinetic energy store?

Answer 54

Anything moving has a kinetic energy store

-energy is transferred to this store when something speeds up and away from this store when something slows down

Question 55

What’s the equation linking Kinetic energy, Speed and Mass?

Answer 55

Kinetic Energy(J) = 0.5 x Mass(kg) x Speed²(m/s)

Question 56

What’s the equation linking Mass, Height, Gravitational potential energy and Gravitational field strength?

Answer 56

Gravitational potential energy(J) = Mass(kg) x Gravitational field strength(N/kg) x Height(m)

Question 57

What’s the gravitational field strength on earth?

Answer 57

10N/kg

Question 58

What’s the transfer of energy of a falling object if there’s no air resistance?

Answer 58

Energy lost from GPE store = Energy gained in kinetic store