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IGCSE PHYSICS MATS > 6) Energy > Flashcards

6) Energy Flashcards

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1
Q

How can energy be stored?

A
  • chemical energy
  • kinetic energy
  • gravitational energy
  • elastic energy
  • thermal energy
  • magnetic energy
  • electrostatic energy
  • nuclear energy
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2
Q

How can energy be transferred?

A
  • mechanically
  • electrically
  • by heating
  • radiation
  • light and sound
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3
Q

Energy cannot be _______ or _________

A
  • created

- destroyed

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4
Q

How would you calculate efficiency?

A

(useful energy transferred/total energy transferred) × 100 = efficiency

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5
Q

What is efficiency calculated in (units)

A

%

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6
Q

How would you draw a Sankey diagram?

A
  • the thickness of the arrows shows how much energy is involved
  • useful energy transfers are shown going left to right
  • wasteful energy transfers are shown going downwards
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7
Q

What are the units for energy?

A

Joules

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8
Q

How can useful energy be calculated?

A

useful energy = mg∆h
m = mass (kg)
g = gravity (N)
∆h = change in height (m)

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9
Q

How is thermal energy transferred along a metal block?

A
  • particles vibrate and pass on this energy to the surrounding particles
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10
Q

What is a convection current?

A
  • gas molecules absorb heat energy from heater, the gas expands becoming less dense
  • the warmer gas is less dense than the surrounding air so it rises to the ceiling
  • as the gas loses heat to its surroundings it becomes more dense
  • the cooler, denser gas sinks towards the ground
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11
Q

Describe the convection current in a refrigerator:

A
  • air at the top of the fridge transfers some of its thermal energy to the ice box and cools down
  • the cooler air is more dense than the surrounding air so it descends down through the shelves on the fridge
  • the cold air absorbs thermal energy from food products in the fridge and becomes warmer
  • the warmer air is less dense than the surrounding air and it rises up through the fridge towards the ice box
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12
Q

What can you say about conduction in metals and gases?

A

metals - good conductors

gases - insulators or poor conductors

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13
Q

How is energy conducted through a non-metallic solid?

A
  • non-metallic solids conduct electricity through the vibrations of the particles to neighbouring particles
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14
Q

Why are metals very good conductors?

A
  • particles are close together

- delocalised electrons in lattice

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15
Q

Name some ways of reducing the heat loss from a house

A
  • carpets
  • double glazing
  • wall insulation
  • loft insulation
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16
Q

Why does warmer water rise upwards in a convection current?

A
  • water heated - expands - lower density than surrounding water therefore rises
17
Q

Which emits more radiation: a hot object or a cold object?

A
  • hot object
18
Q

Which emits more radiation: a dull black object or a shiny bright object?

A
  • a dull black object
19
Q

Which absorbs more radiation: a dull black object or a shiny bright object?

A
  • dull black object
20
Q

Why are shiny bright objects bad radiation absorbers and emitters?

A
  • the shiny surface reflects the radiation
21
Q

How does a vacuum or ‘thermos’ flask keep hot drinks hot (or keep ice-cream cold)?

A
  • it does this by stopping or reducing the transfer of heat by conduction, convection and radiation.
22
Q

What design features reduce conduction in a vacuum flask?

A
  • plastic stopper
  • vacuum (poor conductor)
  • glass
  • plastic case
23
Q

What design features reduce convection in a vacuum flask?

A
  • the stopper

- the vacuum

24
Q

What design features reduce radiation in a vacuum flask?

A
  • silvering
25
Q

How would you calculate work done?

A 
W = F × d
W = work done (joules)
F = force (N)
d = distance moved (m)
26
Q

How would you calculate power?

A 
P = W/t
P = power (J/s) (Watts)
W = work done (J)
t = time taken (s)
27
Q

How would you calculate GPE?

A 
GPE = m × g × h
GPE = gravitational potential energy (J)
m = mass (kg)
g = gravitational field strength (N/kg)
h = height (m)
28
Q

How would you calculate kinetic energy?

A 
KE = 1/2mv²
KE = kinetic energy (J)
m = mass (kg)
v² = speed² (m/s)

IGCSE PHYSICS MATS (7 decks)

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