Energy transfer, efficiency, and thermal energy

Question 1

Name the 8 energy stores

Answer 1

Thermal, kinetic, GPE, EPE, chemical, magnetic, electrostatic, nuclear

Question 2

What is the equation to work out kinetic energy?

Answer 2

KE = 1/2 x mv squared

Question 3

What is the equation for EPE?

Answer 3

EPE = 1/2 x ke squared

Question 4

What is specific heat capacity?

Answer 4

The measure of how much energy a substance can store

Question 5

What is the formula for shc

Answer 5

change in thermal energy = mass x specific heat capacity x temp change

Question 6

What is the equation linking power, energy and time

Answer 6

power = energy/time

Question 7

What is the equation linking power work done and time ?

Answer 7

power = work done/time

Question 8

What is conduction?

Answer 8

The process where vibrating particles transfer energy to neighbouring particles. Occurs mainly in solids.

Question 9

What is thermal conductivity?

Answer 9

measure of how quickly energy is transferred through a material

Question 10

What is convection

Answer 10

Where energetic particles move away from hotter to cooler regions. Occurs only in liquids and gasses.

Question 11

How do radiators work?

Answer 11

Energy is transferred from the radiator to the nearby air particles by conduction . The air by the radiator becomes warmer and less dense as the particles move quicker. This warm air rises and is replaced by cool air. The cooler air is then heated by the radiator. At the same time, the previousl heated air transfers energy to the surroundings . Cycle repeats, causing flow of air around the room - convection current

Question 12

What is the equation for efficiency?

Answer 12

Efficiency = useful power output/ total power input.

Question 13

What is a system?

Answer 13

an object or group of objects

Question 14

what happens when energy transfers occur in a close system?

Answer 14

the net energy change of the system is zero

Question 15

The higher the object is lifted…?

Answer 15

the more energy is transferred to this store

Question 16

Method for specific heat capacity?

Answer 16

1) Measure mass of block, then wrap in insulating layer to reduce energy transferred from block to surroundings. Insert thermometer and heater
2) Measure initial temp of block and set power supply to 10V. Turn on and start stopwatch
3) Current in the circuit does work on the heater, energy transferred electically from power supply to heater’s thermal energy store. Transferred to material’s thermal energy store by heating causing the material’s temperature to increase.
4) As block heats up, use thermometer to meausre its temp
5) do specific heat capacity equation
6) repeat

Question 17

Conservation of energy principle?

Answer 17

Energy can be transferred usefully, stored or dissipated but can never be created or destroyed

Question 18

How to reduce friction\/

Answer 18

Lubricant reduces friction so they can flow easily between objects and coat them.

Question 19

How to reduce energy transfers by heating?

Answer 19

Thermal insulation. Thick walls means low thermal conductivity

Question 20

conduction only happens in…?

Answer 20

solids

Question 21

convection only occurs in…?

Answer 21

liquids and gases

Question 22

Method for investigating energy transfers?

Answer 22

1) Boil water in a kettle. Pour some into a sealable container. Measure mass of water in container
2) Use a thermometer to measure initial temp of water
3) Seal container and leave for 5 mins- use stopwatch
4) Remove lid and measure final temperature
5) pour away water and allow container to cool to room temperature
6) repeat experiment but wrap container in different material