Topic 1 - Energy

Question 1

name all of the energy stores you need to know:

Answer 1

thermal
kinetic
gravitational potential
elastic potential
chemical
magnetic
electrostatic
nuclear

Question 2

how is energy transferred?

Answer 2

mechanically
electrically
by heating or by radiation

Question 3

how is energy transferred mechanically?

Answer 3

by a force doing work

Question 4

how is energy transferred electrically?

Answer 4

work done by moving charges

Question 5

how is energy transferred by heating or radiation?

Answer 5

e.g. light or sound

Question 6

what is a system?

Answer 6

a word for a single object or group of objects that you’re interested in

Question 7

what happens when a system changes?

Answer 7

energy is transferred

Question 8

how can energy be transferred in a system?

Answer 8

into or away from the system
between different objects in the system
between different types of energy stores

Question 9

what are closed systems?

Answer 9

systems where neither matter nor energy can enter or leave. the net change in the total energy of a closed system is always 0

Question 10

how is energy transferred when boiling water in a kettle?

Answer 10

when the water is the system, energy is transferred to the water by heating into the waters thermal energy store
if the kettle and the water is a two object system, energy is transferred electrically to the thermal energy store of the kettle, which transfers to the waters thermal energy store by heating

Question 11

whats another word for work done?

Answer 11

energy transferred

Question 12

how can work be done?

Answer 12

when current flows or by a force moving an object

Question 13

examples of work being done:

Answer 13

the initial force of someone throwing a ball upwards, kinetic -> gravitational
a ball dropping from a height, the gravitational force does work, gravitational -> kinetic
the friction between a cars breaks and its wheels kinetic -> thermal

Question 14

what does anything moving have?

Answer 14

energy in its kinetic energy store. energy is transferred to this store when an object speeds up and away from it when it slows down.

Question 15

what does the amount of energy in the kinetic energy store depend on?

Answer 15

the objects mass and speed. the greater the mass the faster it goes, the more kinetic energy

Question 16

what is the formula for kinetic energy?

Answer 16

KE = 1/2mv²

Question 17

what happens when an object is lifted in a gravitational field?

Answer 17

it requires work, this causes an energy transfer to the gravitational energy store. the higher the object the more energy in the GPE store

Question 18

what does the amount of energy in the GPE store depend on?

Answer 18

the objects mass, its height and the strength of the gravitational field.

Question 19

what is the equation for gravitational potential energy?

Answer 19

GPE = mgh

Question 20

what energy transfers happen when an object falls?

Answer 20

energy is transferred from its gravitational energy store to its kinetic energy store. air resistance also transfers energy into other stores like thermal energy of the surroundings

Question 21

what happens if something falls if there’s no air resistance ?

Answer 21

energy lost from GPE store = energy gained in the kinetic energy store

Question 22

when will energy be transferred to the elastic potential store?

Answer 22

stretching or squashing an object

Question 23

how can the energy in the elastic potential energy store be found?

Answer 23

EPE=1/2ke²

elastic potwntial energy= 1/2 x spring constant x extension²

Question 24

what is specific heat capacity?

Answer 24

the amount of energy needed to raise the temperature of 1kg of a substance to 1*C

Question 25

what is the equation that links SHC and energy transferred?

Answer 25

ΔE=mcΔθ | change in thermal energy = mass x SHC x change in temperature

Question 26

how to investigate specific heat capacity of a solid object?

Answer 26

get a block of the material with 2 holes in it measure it then wrap it in a insulating layer insert heater and thermometer measure initial temp then turn on power supply to 10V and start stop watch take readings of temperature and current every minute for 10 minutes the current shouldn't change

Question 27

for an investigation on SHC why does the object need an insulating layer?

Answer 27

to reduce the energy transferred to the surroundings

Question 28

how does the heater heat the block in a SHC investigation?

Answer 28

when the power supply is turned on the current in the circuit does work on the heater, transferring energy electrically to the heaters thermal energy store, this is then transferred to the materials thermal energy store, so its temperature increases

Question 29

how can you work out the energy transferred to the heater at each interval in a SHC investigation?

Answer 29

use the current and potential difference to find power using P=IV then use E=Pt to find the amount of energy transferred at each interval

Question 30

how to find specific heat capacity from the results of a specific heat capacity graph?

Answer 30

assuming all the heat from the heater was transferred to the material, you can plot a graph of energy transferred by temperature. the gradient is Δθ/ΔE so the specific heat capacity = 1/(gradient x mass of material)

Question 31

what is the conservation of energy principle?

Answer 31

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

Question 32

what is an example of energy being wasted?

Answer 32

in phones energy is usefully transferred from the chemical energy store of the battery but some is dissipated by transferring to thermal energy stores

Question 33

example of energy transfers for a closed system:

Answer 33

cold spoon dropped into insulated flask of hot soup, which is then sealed. this forms a closed system energy is transferred from thermal energy store of soup to useless thermal energy store of spoon. net change of energy is 0 but soup cools slightly

Question 34

what is power?

Answer 34

the rate of energy transfer, or the rate of doing work. measured in watts

Question 35

what equations can be used to find power?

Answer 35

P=E/t | P=W/t

Question 36

what does increasing power do?

Answer 36

it doesn't mean more energy is transferred at once but that the same amount of energy is transferred in less time