P7

Question 1

What is a chemical energy store?

Answer 1

Eg: glucose in your muscles with oxygen
Energy between chemical bonds

Question 2

What is gravitational energy store?

Answer 2

A skier at the top of a hill
E= m✖️g(10N/kg)✖️h

Question 3

What is a nuclear energy store?

Answer 3

Hydrogen from the sun
E = m ✖️velocity of light squared

Question 4

what is power?

Answer 4

the rate of energy transfer

P= E/T
1 Watt = 1 joule per second

Question 5

what is the kilowatt hour kWh?

Answer 5

a convince unit used for the measure of energy

1kWatt is used within an hour

Question 6

Is having a device with a high power cheaper to run? (6 points)

Answer 6

. higher power devices transfer elecetrical energy faster to other forms
.in the same time they will use more energy
. so will cost more
.however if it is more efficent
. it won’t need to be on for a long amount of time
. so may use less energy , costing less money

Question 7

what is the law of conservation of energy?

Answer 7

energy can not be created or destroyed only transferred

Question 8

what is a thermal energy store?

Answer 8

the vibrations of the particles in the object. In hotter objects, the particles vibrate faster.

E=Mcø

Question 9

what is a kinetic energy store?

Answer 9

associated with a moving objecting

E = 1/2 m v²

Question 10

what is a gravitational energy store?

Answer 10

an object at height

E= m g h
(g=10N/kg)

Question 11

what is a elastic energy store?

Answer 11

when an object is stretched, squashed or twisted

E= 1/2 k e²

Question 12

what is the efficiency equation?

Answer 12

USEFUL output energy transfer/ input energy transfer

Question 13

what are wasted energy transfers ?

Answer 13

transfers that you didn’t want to happen , eg:heat being transferred to the surroundings

Question 14

when will a thermal energy transfer occur?

Answer 14

when there is an energy difference between two points

Question 15

when is energy transferred to the surroundings as heat ?

Answer 15

when a system is not closed (external forces are acting on it)

Question 16

why is energy from the surroundings not useful?

Answer 16

it cannot be easily transferred to operate a task

Question 17

what does the rate of heat energy , between walls depend on?

Answer 17

temperature gradient
area of walls
thickness of walls
material of wall(thermal conductivity)

Question 18

how does the area of walls affect energy transfer?

Answer 18

the greater the area of the walls, the greater the rate of heat energy transfer

Question 19

how does the thermal conductivity of walls affect the energy transfer?

Answer 19

the lower the thermal conductivity, the (better)less heat loss

Question 20

what is thermal conductivity ?

Answer 20

the heat energy transfered per second through a 1m thick wall , of area 1m² whe a temperature difference of 1 degree exist

Question 21

why would you want to reduce heat loss?

Answer 21

more cost effective (heating)

Question 22

how do you improve the efficiency of a friction causing heating?

Answer 22

lubricate the part

Question 23

how do you improve the efficiency of a wire causing heating?

Answer 23

choose a wire with a small resistance

Question 24

how do you improve the efficiency of air resistance causing heating of vehicles?

Answer 24

make it more steamline

Question 25

how do you improve the efficiency of a machines causing sound?

Answer 25

tighten loose parts to reduce vibration