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Question 1

State all possible energy stores.(8)

Answer 1

Kinetic - anything moving has energy in its kinetic energy store
Thermal - any object, the hotter it is the more energy in this store
Chemical - anything that can release energy via chemical reaction
Gravitational Potential - anything in a gravitational field
Elastic Potential - anything stretched, like a spring
Electrostatic - two charges that attract or repel each other
Magnetic - two magnets that attract or repel each other
Nuclear - nuclei releasing energy in nuclear reactions

Question 2

State the four transfers that energy can be transferred.(4)

Answer 2

Mechanical work - a force moving an object through a distance
Electrical work - charges moving due to a potential difference
Heating - due to temperature difference caused electrically or by chemical reaction
Radiation - energy transferred as a wave, eg light and infrared the Sun emits light radiation and infrared radiation.

Question 3

Define Conservation of Energy.(2)

Answer 3

Energy can be stored, transferred between stores and dissipated but it can never be created or destroyed.

Question 4

What is convection?(2)

Answer 4

Convection is the movement of particles through a substance, transporting their heat energy from hotter areas to cooler areas(in fluids).
This is because as particles heat up, they expand which makes them less dense(their volume increases and the mass is the same), and so they rise over the more dense particles.
In turn this creates a convection current where the bottom of a room is cooler than the top.

Question 5

What is thermal radiation in terms of thermal energy transfers?(3)

Answer 5

Radiation relies on not particles, but infrared radiation; therefore it can pass through a vacuum.
When infrared radiation is absorbed by an object its temperature rises.
It should also be noted that black, matt objects are much better emitters than white, shiny ones. Therefore, black matt objects will heat up much quicker but also cool down much quicker.

Question 6

What is conduction and why is it more efficient in metals?(4)

Answer 6

Conduction is when particles vibrate and collide with other particles, transferring energy through an object.
All materials have thermal conductivity but metals have a high thermal conductivity compared to other materials.
This is because in metals and other good conductors, collisions are not only caused by vibrations passing from atom to atom; they are also caused by collisions between fast moving free electrons and metal ions.
Conduction by collisions between fast moving free electrons is much faster than conduction by passing vibrations from atom to atom.

Question 7

What is the effect of lubrication on energy transferred by friction?(2)

Answer 7

Lubricants can be used to reduce the friction between objects surfaces when they move.
This reduces the amount of work to the thermal energy store of an object.

Question 8

Formula for Gravitational Potential Energy?

Answer 8

G.P.E = mgh

Question 9

Formula for Kinetic Energy?

Answer 9

KE = 1/2(m)(v^2)

Question 10

Formula for work done?

Answer 10

Work done(Joules) = (force)(distance moved)

Question 11

Formula for power?

Answer 11

Power(Watts) = work done/time

Question 12

How does insulation reduce unwanted energy transfer?(2)

Answer 12

Radiation can happen in a vacuum, so it is very hard to prevent that type of heat transfer occurring, however convection and conduction can be reduced via insulation.
Insulation often uses materials with lots of trapped air in, such as wool or foam, to reduce the vibration across particles and stop a convection current.

Question 13

Define a renewable energy source and provide examples.

Answer 13

An energy source that can be replenished at a faster rate than the rate at which it is being used.
These include: Solar cells, solar heating systems, wind, biofuel, hydroelectricity, geothermal, tidal.

Question 14

Describe how electricity is generated from wind?(2)

Answer 14

Wind turbines are used which spin, and using the generator effect to create electricity.
They can be on land or on water, and when on land the space can still be used for other things. However, they are very noisy and can be unreliable.
Kinetic energy » Electrical energy.

Question 15

Describe how electricity is generated from solar cells, and separately solar heating systems?(3)

Answer 15

In solar panels using solar cells, photovoltaic cells use light to create electricity, this light being from the sun.
In solar heating systems, a panel is often directed at the sun and a tank which heats up water.
They are good for producing electricity in remote locations, but often require masses of space and are unreliable.
Both processes: Thermal energy » Electrical energy.

Question 16

Describe how electricity is generated from geothermal resources?(2)

Answer 16

Heat from underground caves can be used to create steam, which spins turbines creating electricity.
Geothermal stations are reliable and relatively small scale. However, they can release harmful gases from underground.
Thermal energy » Kinetic energy » Electrical energy.

Question 17

Describe how electricity is generated from water?(4)

Answer 17

With tidal water, a dam is used to trap seawater at a high tide which can then be released through a turbine to generate electricity. Tides are big, predictable and so can produce large amounts of electricity at regular intervals. However, is only suitable at certain locations.
Hydroelectric systems use the gravitational potential energy of water stored is reservoirs to turn turbines which generate electricity.
This is very reliable and can produce big amounts of electricity in short notice. However, can involve flooding large areas of wildlife.
(G.P.E »)Kinetic energy » Electrical energy.