energy Flashcards

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1
Q

what is the waste energy normally

A

heat

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2
Q

what is the following for a car:

energy input
useful energy
waste energy

A

input= chemical

useful= kinetic

waste= heat and sound

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3
Q

what is the following for a lamp:

energy input
useful energy
waste energy

A

input- electrical
useful- light
waste- heat

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4
Q

what’s a sankey diagram

A

diagram to summarise electrical transfers taking place

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5
Q

can energy be created or destroyed

A

no it can be stored, dissipated or transferred usefully

called conversion of energy

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6
Q

how to work out the waste energy from a sankey diagram

A

useful energy- total energy

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7
Q

what happens to waste energy

A

heat energy flows away from a hotter object to its cooler surroundings

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8
Q

what is the efficiency

A

the proportion of energy supplied

transferred in useful ways

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9
Q

how to calculate effientcy

A

efficiency= useful energy out/ total energy out

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10
Q

what is useful energy

A

energy transmitted to where it is wanted, in the form it is wanted

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11
Q

what is wasted energy

A

energy that isn’t usefully transmitted

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12
Q

what energy spreads out into its surroundings

A

useful

wasted

and it becomes less useful as it spreads out, may heat up surrounding air

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13
Q

what is weight measured in

A

newtons

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14
Q

what is energy measured in

A

joules

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15
Q

why do machines waste energy

A
  1. friction between moving parts
  2. wires get hot
  3. air resistance
  4. sound created by machinery
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16
Q

what happens to surroundings when useful and wasteful energy is transferred

A

surroundings become warmer

17
Q

name a problem with energy as it dissipates (spreads out)

A

it gets more and more difficult to use for further energy transfers

18
Q

name some different forms of energy

A
  1. chemical energy (fuel)
  2. kinetic energy (moving)
  3. Gravity potential energy
  4. elastic potential energy
  5. electrical energy
19
Q

can energy change from one form to another

A

yes eg

chemical energy in battery turns into electrical energy which turns into light energy which turns into energy heating surroundings

20
Q

what happens to an objects gravitational potential energy and kinetic energy when it falls

A

when when an object falls and gains speed
its gravitational potential energy decreases
and it’s Kinetic energy increases

21
Q

what is the conservation of energy

A

result meaning energy cannot be created or destroyed

conservation of energy applies to all energy changes

22
Q

how can you make machines more efficient

A

reduce

friction
air resistance
electrical resistance
noise

23
Q

can a machine be more than 100% efficient

A

no a machine can’t get more energy out that is put into it

24
Q

what 3 ways can hear be transferred by

A
  1. radiation
  2. conduction
  3. convection
25
Q

what is heat radiation

A

the transfer of heat energy by infrared radiation

26
Q

what form of energy is coal

A

chemical

27
Q

how is chemical energy in food transferred into someone lifting a bar

A

chemical in porridge > kinetic in muscles> kinetic in moving bar