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GCSE Physics > Energy > Flashcards

Energy Flashcards

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1
Q

8 stores of energy?

A
  1. Kinetic
  2. Thermal
  3. Chemical
  4. Nuclear
  5. Elastic Potential energy
  6. Gravitational Potential Energy
  7. Magnetic
  8. Electrostatic
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2
Q

Energy must be transferred to do what?

A

Work

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3
Q

What are the 4 ways to transfer energy?

A
  1. Radiation
  2. Electrically
  3. Mechanically
  4. Heat
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4
Q

Where does the earths energy come from?

A

The sun - transferred by radiation

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5
Q

Definition of transfer by radiation?

A

When energy is transferred as sound, light (not touching anything) - not electrically, mechanically or by heating :)

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6
Q

Definition of energy transferring electrically?

A

When energy is transferred through currents

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7
Q

Definition of transfer by heating?

A

When energy is transferred as objects heat up

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8
Q

Definition of mechanical transfers of energy?

A

When energy is transferred by parts moving

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9
Q

Law of Conservation of energy?

A

Energy cannot be created or destroyed, only transferred from one type to another

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10
Q

What is energy measured in?

A

Joules

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11
Q

What is work?

A

Energy transferred

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12
Q

equation for work done =

A

work done (J) = force (N) * distance (m)

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13
Q

Weight =

A

weight (N) = mass (Kg) * gravity (9.8 n/kg)

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14
Q

GPE =

A

GPE (J) = (mass (Kg) * gravity(9.8 n/kg) - weight) * height (m)

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15
Q

KE =

A

KE (J) = 0.5 * M (Kg) * (v*v) (m/s)

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16
Q

EPE =

A

EPE (J) = 0.5 * k (N/M) * (x*x) (M)

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17
Q

What happens when a system changes?

A

Energy is transferred

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18
Q

What is a system?

A

A single object or group of objects of interest

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19
Q

What is a closed system?

A

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

20
Q

Work can be done when (2) ?

A
  1. Current flows

2. Force moves an object

21
Q

What is kinetic energy?
How can you increase the KE of an object?
When is KE transferred to and away from an object?

A

Anything that moves has kinetic energy
Increasing an objects mass or speed increases KE
When an object speeds up, KE is transferred to this store, when an object slows down, KE is transferred away

22
Q

What is GPE?
How can you increase the GPE of an object?
When is GPE transferred to and away from an object?

A

GPE is energy an object has based on its position above the earths surface
Increasing the objects mass, height, or the strength of the gravitational field the object is in increases its GPE
The higher an object is lifted, the more energy is transferred to the store, the more the object is lowered, the more GPE transfers away from the store

23
Q

What is EPE?

How can you increase the EPE of an object?

A

Elastic potential energy is energy stored as a result of applying a force to deform (stretch/squash) an elastic object
EPE is dependant on the length the object is stretched and the spring constant

24
Q

What does efficiency tell us?

A

It tells us how much of the energy put in is transferred usefully

25
Q

Efficiency =

A

efficiency(%) = useful energy output/total energy input* 100

note - efficiency equation can be done in terms of power

useful power output (W) / total power output (W)
* 100

26
Q

What is Power?

A

Power is how much work is done per second - measure in Watts

27
Q

Power =

A

Power (W) = work (J) / time (S)

28
Q

1 W =

A

1 J per second

29
Q

What is useful energy?

A

Energy transferred to where it is wanted in the way it is wanted

30
Q

What is wasted energy?

A

Energy that is not usefully transferred

31
Q

Energy that is not transferred usefully is…

A

dissipated

32
Q

Why do devices waste energy? (4)

A
  1. Friction between moving parts causes heating
  2. The resistance of a wise causes the wire to get hot when current passes through it
  3. Air resistance causes a force on a moving object that opposes its motion
  4. Sound created by machinery causes energy transfer to the surroundings
33
Q

How to reduce wastes of energy (4)?

A
  1. Lubricate moving parts to avoid friction
  2. Uses wires in circuits with as little electrical resistance as possible
  3. Streamline objects to reduce air resistance
  4. Cut out noise by tightening loose parts for example
34
Q

energy changes when an is object projected upwards

A

Energy of the object starts of by being stored as kinetic energy, it slows down as it increases in height because the KE is transferred to GPE

35
Q

energy changes when an moving object hits an obstacle

A

energy shifts from kinetic store of object to the thermal energy store of object and obstacle

36
Q

energy changes when an object accelerates at a constant force

A

energy shifts from chemical store of the fuel to the kinetic store of the object

37
Q

energy changes when a object slows down

A

energy shifts from the kinetic store of the vehicle to the thermal store of the brakes and surroundings

38
Q

energy changes when bringing water to boil in an electric kettle

A

energy shifts from chemical store (in the electricity) to the thermal store of the water

39
Q

Light bulb useful energy and wasted energy?

A

useful: light emitted from the glowing filament
wasted: energy transferred from the filmet heating the surroundings

40
Q

Electric heater useful energy and wasted energy?

A

useful: Energy heating surroundings
wasted: Nothing really (some light emitted from glowing element)

41
Q

Electric toaster useful energy and wasted energy?

A

useful: energy heating bread
wasted: energy heating the toaster case and surrounding air

42
Q

Electric kettle useful energy and wasted energy?

A

useful: Energy heating water
wasted: Energy heating kettle itself

43
Q

Hairdryer useful energy and wasted energy?

A

useful: kinetic energy of air driven by fan and energy heating air flowing past heating element
wasted: Sound of fan motor energy heating hairdryer itself

44
Q

Electric motor useful energy and wasted energy?

A

useful: kinetic energy of objects driven by motor, GPE potential energy of object lifted by motor
wasted: energy heating the motor and energy transferred as sound

45
Q

What is the spring constant? What is extension?

A

The spring constant, k, is a measure of the stiffness of the spring - the higher the k, the stiffer the spring
The increased length of an object when stretched is the extension, it is equal to:
new length - original length

46
Q

What is the limit of proportionaltiy?

A

The limit of proportionality refers to the point beyond which Hooke’s law is no longer true when stretching a material. The elastic limit of a material is the furthest point it can be stretched or deformed while being able to return to its previous shape. Once a material has gone past its elastic limit, its deformation is said to be inelastic.

GCSE Physics (5 decks)

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