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Physics > Energy > Flashcards

Energy Flashcards

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Physics 101 flashcards AP® Physics flashcards
1
Q

Name 4 energy stores

A
  1. Kinetic
  2. Gravitational potential
  3. Magnetic
  4. Electrostatic
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2
Q

3 ways energy can be transferred in a system?

A
  1. In or out the system
  2. To and from different objects
  3. To and from different stores
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3
Q

What is a closed system

A

Matter nor energy can leave or enter

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4
Q

What is always the net change in the total energy of a closed system?

A

0

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5
Q

2 ways energy can be transferred and how?

A
  1. Heating - energy is transferred into the water’s thermal energy store from the kettle’s heating element
  2. Doing work - transfers energy by providing a force
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6
Q

Equation for kinetic energy store?

A

E = 1/2mass x velocity^2

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7
Q

How does kinetic energy transfer?

A

When an object speeds up, energy is transferred to this store, when an object slows down, energy is transferred away

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8
Q

Equation for GPE

A

E = mass x gravitational field strength x height

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9
Q

How do falling objects transfer energy?

A

Energy from the object’s GPE store is transferred into the object’s kinetic store

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10
Q

Why does energy lost from GPE = energy gained in kinetic not always work for falling objects?

A

Air resistance causes some energy to be transferred to other energy stores

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11
Q

Equation for elastic potential energy?

A

E = 1/2spring constant x extension^2

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12
Q

Equation for specific heat capacity?

A

Change in energy = mass x specific heat capacity x temperature change

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13
Q

What is specific heat capacity?

A

The amount of energy needed to heat 1kg of an object up by 1 degree Celsius

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14
Q

What is the conservation of energy principle?

A

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

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15
Q

How can energy be dissipated?

A

In a phone, energy from the battery’s chemical store is usefully transferred, whilst some is transferred to the thermal energy store

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16
Q

What is wasted energy?

A

Energy being stored in a way that is not useful

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17
Q

Describe energy transfer in a closed system of a spoon in soup.

A

Assuming a lid is a perfect insulator, energy is dissipated from the thermal energy store of the soup to the useless thermal store of the spoon, cooling the soup down, although no energy has left the system

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18
Q

Equation for power?

A

P = energy transferred (or work done) / time

19
Q

What does power mean?

A

Rate of energy transfer

20
Q

How does conduction work?

A
  1. Energy is transferred to an object’s thermal energy store by heating
  2. Particles in this part of the object begin vibrating and collide with adjacent particles, transferring to kinetic energy stores
21
Q

What is thermal conductivity?

A

How quickly energy is transferred through an object

22
Q

How does convection work?

A
  1. Energy is transferred to a liquid/ gases thermal energy store by heating
  2. The faster moving particles then move further apart, reducing density
  3. The less dense substance, then moves above the denser, cooler substance
23
Q

How do radiators heat rooms?

A
  1. Energy is transferred from the radiator to nearby air particles by conduction
  2. Air particles by the radiator move quicker and spread out, reducing density and moving above the denser air
  3. Colder takes the place of the hot air and a convection current is created
24
Q

How do lubricants reduce unwanted energy transfer?

A

Lubricants reduce friction, which can cause some energy to be dissipated to an object’s thermal store

25
Q

4 ways energy loss can be prevented in houses?

A
  1. Cavity walls - have an air gap to reduce energy loss through conduction out of the house
  2. Loft insulation - reduce convection currents in a loft
  3. Double glazed windows - air gap between two windows reduces conduction
  4. Draught excluders - reduce convection around doors and windows
26
Q

Efficiency equation?

A

Efficiency = useful energy output/ total energy input

27
Q

What does efficiency mean?

A

How much energy is transferred usefully

28
Q

Example of a 100% efficient device?

A

Electric heater

29
Q

Non renewable energy sources used in transport?

A
  1. Petrol/ diesel
  2. Coal
30
Q

Renewable energy sources used in transport?

A

Biofuel

31
Q

Non renewable energy sources used for heating

A
  1. Natural gas
  2. Coal
  3. Electric heaters
32
Q

Renewable energy sources used for heating?

A
  1. Geothermal
  2. Solar water heaters
  3. Bio fuel
33
Q

4 Disadvantages of wind power?

A
  1. Spoil the view
  2. Noise pollution
  3. Unreliable - must be windy
  4. Impossible to increase supply in high demand
34
Q

3 Disadvantages of solar cells?

A
  1. Expensive to manufacture
  2. Can’t increase supply in high demand
  3. Only work in the daytime
35
Q

2 Disadvantages of geothermal?

A
  1. Not many suitable locations
  2. Expensive to build a plant
36
Q

3 Disadvantages of hydroelectric?

A
  1. Flooding valleys destroys habitats
  2. Can ruin landscapes
  3. Initial costs are high
37
Q

3 Disadvantages of waves?

A
  1. Disturbed sea bed and habitat destruction
  2. Hazard to boats
  3. Unreliable - waves rely on wind
38
Q

Disadvantages of tidal barrages?

A
  1. Preventing access to boats
  2. Ruins habitats
  3. Spoils view
39
Q

Disadvantages of bio fuels?

A
  1. Only carbon neutral if plants are grown at the same rate as burning
  2. Cannot respond to immediate energy demands
  3. Plants for bio fuels means less space for people to grow foods
40
Q

Advantages of non renewable energy?

A
  1. Reliable
  2. Can increase supply in times of high demand
  3. Running costs are low
41
Q

4 Environmental disadvantages of non renwable energy?

A
  1. Greenhouse effect
  2. Sulphur dioxide causes acid rain which damages wildlife
  3. Oil spills kill marine life
  4. Nuclear waste is very dangerous
42
Q

Why does the UK aim to be more renewable?

A

Pressure from other countries and the public

43
Q

Why is renewable use limited?

A
  1. Scientists can’t make people change
  2. Renewable plants mean higher costs for the population through tax
  3. Ethical arguments of making people live next to wind farms

Physics (8 decks)

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