energy transfers

Question 1

when energy is transferred to an object hows it transferred

Answer 1

when energy is transferred to one of the objects energy stores

Question 2

what are the 4 energy stores

Answer 2

kinetic, thermal, chemical, gravitational potential, elastic potential, electrostatic, magnetic and nuclear

Question 3

work done is another way of saying..

Answer 3

energy transfer

Question 4

how can energy be transferred in four main ways

Answer 4

mechanically e.g. making an object move by exerting a force on it
electrically e.g. electrons moving around an electric circuit
heating e.g. heating up water in a kettle
radiation e.g. energy from the sun is transferred via light waves

Question 5

if you lift a ball up high what energy are you transferring. Then if you drop the ball hows energy transferred

Answer 5

if i lift a ball up high your transferring energy mechanically from the chemical energy store in my arm to the balls gravitational potential store. if i drop the ball energy is transferred mechanically due to the force of gravity to the balls kinetic store

Question 6

whats a system another word for

Answer 6

a system is just another word for a single object

Question 7

what are closed systems

Answer 7

closed systems are systems where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero

Question 8

whats the conservation of energy principle

Answer 8

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

Question 9

whats dissipated energy

Answer 9

another word for wasted energy

Question 10

anything which is moving has energy in its..

Answer 10

kinetic energy stores. if the object speeds up energy is transferred into that store, if the object is slowed down energy is transferred away

Question 11

a moving object will have a … and…

Answer 11

a moving object will have a mass (kg) and velocity (m/s) (speed in a given direction)

Question 12

equation for kinetic energy and triangle

Answer 12

Ek = 1/2mvsquared
Ek on top of the triangle, 1/2 on the left bottom, m next to 1/2 and vsquared on the right

Question 13

whats kinetic energy measured in

Answer 13

joules (J)

Question 14

how to get from g to kg

Answer 14

divide by 1000

Question 15

how to get from kg to g

Answer 15

x 1000

Question 16

what does lifting an object cause a transfer of…

Answer 16

lifting an object in a gravitational field requires work. this csauses a transfer of energy to the gravitational potential energy (g.p.e) store

Question 17

whats the symbol for energy transfer

Answer 17

Ep

Question 18

what 3 things does the amount of energy transferred (Ep) depend on

Answer 18

the objects mass (m). this is ALWAYS in kg (so convert when needed)
the strength of the gravitational field (on earth that is 9.8N/Kg, this means that for every 1kg of mass, gravity pulls down on that object with a force of 9.8N (g)
the height e.g. how high the object is lifted (h) this is always in metres (so convert if needed)

Question 19

whats the equation from gravitational potential energy (j) and units
how do u put it in a triangle

Answer 19

EP = mgh
m=kg g=N/Kg h = m
Ep at the top m on the bottom left g in the middle bottom h on the right

Question 20

e.g. a 50 kg mass is raised 6.0m above the ground. How much energy was transported to the g.p.e store if the gravitational field strength was 9.8N/Kg

Answer 20

50x9.8x6.0
=2490J

Question 21

energy lost from the g.p.e store =

Answer 21

energy lost from the g.p.e store - energy gained in the kinetic energy store

Question 22

Ep =?

Answer 22

Ep = Ek

Question 23

a man with a mass of 65kg falls from a height of 2m. If the gravitational field strength is 9.8N/Kg how fast is he falling

Answer 23

ep = mgh
65x9.8x2=1247J
ek = 1/2mvsquared
=6.2m/s

Question 24

definition of specific heat capacity

Answer 24

specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1degreeC

Question 25

change in thermal energy equation and how to put it in a triangle

Answer 25

Change in thermal energy = mass x specific heat capacity x change in temperature ΔQ = m × c × ΔT

Question 26

Ee is the same as

Answer 26

Ek

Question 27

whats the experiment to investigate the specific heat capacity of a solid material e.g. copper

Answer 27

you first measure the mass of the block of material.once this is done u wrap the block in an insulating material to reduce heat energy transfer to the environment. inserted into the block is a thermometer and an immersion heater. the heater is connected to a power supply which is set to 10v. when power supply is switched on the immersion heater warms up heating the block up.take an initial temp reading,switch the hater on and then leave it for a set period of time e.g.10 mins.after this time u measure the temp of the block again. this current does work on the heater transferring energy electrically from the power supply to the heaters thermal store.the energy is then transferred to the thermal store of the block by heating causing by the temp to increase

Question 28

whats power

Answer 28

power is the rate of energy transfer, or the rate of doing work

Question 29

whats conduction

Answer 29

the process by which vibrating particles transfer energy to neighbouring particles

Question 30

thermal conductivity definition

Answer 30

measure of how quickly energy is transferred through a material this way. the higher the thermal conductivity the quicker the energy is spread out across an object via conduction

Question 31

whats a thermal insulator and thermal conductor

Answer 31

a material with a high thermal conductivity is known as a thermal conductor. A material with a low thermal conductivity id known as a thermal insulator

Question 32

what are things u can use to reduce the amount of energy lost from a building

Answer 32

loft insulation hot water tank jacket double glazing cavity wall insulation draught-proofing

Question 33

whats loft insulation

Answer 33

fibreglass is an insulating material made of thin strands of glass that trap pockets of air. a thick fibreglass wool laid out across the whole loft floor reduces conduction to the attic space,as the material it reduces the energy transfer by convection, by preventing convection currents from forming

Question 34

whats double glazing

Answer 34

double glazed windows work in the same way as cavity walls they have an air gap between 2 sheets of glass to prevent energy transfer by conduction through the windows

Question 35

whats draught proofing

Answer 35

draught excluders or strips of foam or plastic around doors and windows stop draughts blowing in and out, and reduce energy transfer by convection

Question 36

whats hot water tank jacket

Answer 36

putting fibreglass wool around a hot water tank reduces the energy transfer by conduction from the tanks thermal energy store in the same way as loft insulation

Question 37

whats thick curtains do for insulation

Answer 37

big bits of cloth over the window create an air gap between the room and the window,stopping hot air reaching the glass by convection. they also reduce energy transferred by convection

Question 38

how to investigate how effective various materials are as thermal insulators using an experiment

Answer 38

boil water in a kettle. put some of it into sealable container to a safe level. measure mass of the water in the container and use a thermometer to measure the initial temp of water. seal container + leave for 5 mins meausre this time. then remove lid + measure final temp of water. pour away water and allow container to cool to room temp. repeat but each time wrap container in diff material