Energy transfers (4.2 - 4.10)

Question 1

kinetic energy

Answer 1

the energy of a moving object

Question 2

gravitational potential energy

Answer 2

the energy something gains when you lift it up, and which it loses when it falls

Question 3

elastic potential energy

Answer 3

the energy of a stretched spring or elastic band

Question 4

electrostatic energy

Answer 4

the energy due to the force of attraction (or repulsion) between two charges

Question 5

magnetic energy

Answer 5

the energy due to the force of attraction (or repulsion) between two magnets

Question 6

chemical energy

Answer 6

the energy contained in a chemical substance

Question 7

nuclear energy

Answer 7

the energy contained within the nucleus of an atom

Question 8

thermal energy

Answer 8

the energy something has due to its temperature (or state)

Question 9

four ways in which energy can be transferred between stores

Answer 9

mechanically, electrically, heating, radiation

Question 10

mechanically

Answer 10

when a force acts on a body, energy can be transferred between two stores

Question 11

electrically

Answer 11

electricity can transfer energy from a power source, delivering it to components within a circuit

Question 12

heating

Answer 12

thermal energy can be transferred from place to place by the processes of conduction, convection and thermal radiation

Question 13

radiation

Answer 13

light and sound carry energy and so can transfer it between places

Question 14

law of conservation of energy

Answer 14

energy cannot be created or destroyed

Question 15

equation for efficiency

Answer 15

efficiency = useful energy output/total energy output x 100

Question 16

Conduction

Answer 16

• main method of thermal energy transfer in solids
• when a material is heated, the atoms start to vibrate
• as they do, they bump into each other, transferring energy from atom to atom

Question 17

Convection

Answer 17

• main way that heat travels through liquids and gases
• when a liquid or gas is heated, the molecules push each other apart, making the liquid/gas expand
• this makes the liquid/gas less dense than the surroundings
• the hot liquid/gas rises, and the cooler liquid/gas moves in to take its place

Question 18

Thermal radiation

Answer 18

• only way in which heat can travel through a vacuum

- all hot objects give off thermal radiation; the hotter they are, the more they emit

Question 19

ways of reducing unwanted energy transfer

Answer 19

• covering the cold object with a material that will reduce the amount of heat reaching the object
• cover the material with a shiny (non-metal) coating
• putting a lid on a beaker