Using Energy Flashcards

1
Q

What are the different forms of energy?

A
  • Light
  • Heat (thermal)
  • Sound
  • Kinetic
  • Nuclear
  • Electrical
  • Gravitational Potential
  • Elastic Potential
  • Chemical

The last three are forms of stored energy

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2
Q

When is energy most useful?

A

When it can be transfered from one form to another

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3
Q

Energy can be ____________ but it cannot be __________.

A

Energy can be transfered from one form to another but it cannot be created or destroyed.

This is known as the conservation of energy

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4
Q

What happens when an object falls?

A

It gains speed and its gravitational potential energy decreases whilst its kinetic energy increases

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5
Q

What type of energy do all objects above the ground have?

A

Gravitational potential

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6
Q

What does conservation of energy apply to?

A

All energy changes

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7
Q

What is a machine?

A

Something that transfers energy from one place to another or from one form to another

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8
Q

What does the energy we get out of a machine consist of?

A

Useful energy, which is transfered to the place we want in the form we want.

Wasted energy, which is not usefully transfered.

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9
Q

Where will both useful and wasted energy eventually be transfered?

A

To the surroundings, causing them to heat up

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10
Q

What happens when energy is transfered to the surroundings.

A

They heat up and the energy spreads out. This makes it more difficult to use for further energy transfers

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11
Q

How is energy often wasted?

A

Because of friction between moving parts of a machine. The energy warms up the machine and the surroundings.

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12
Q

When might friction be useful?

A

In the brakes of a bike/car.

The kinetic energy of the vehicle is transfered to heat energy heating the brakes and thus slowing the vehicle.

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13
Q

What is the energy supplied to a machine known as?

A

The input energy

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14
Q

What do we know about the relationship between the input energy and the output energy?

A

input energy = useful energy + wasted energy

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15
Q

What makes a machine more efficient?

A

The less energy a machine wasted, the more efficient it is

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16
Q

Can an appliance every be 100% efficient?

A

Yes! But there’s only one - an electric heater

17
Q

How is an electric heater 100% efficient?

A

It usefully transfers all of its electrical energy input energy to thermal energy, thus heating its surroundings (which isn’t wasteful because that’s what it’s designed to do)

18
Q

What measures can be taken to make machines more efficient?

A

Machines can be made more efficient by reducing:

  • Friction
  • Air resistance
  • Electrical resistance
  • Noise due to vibrations
19
Q

Draw a Sankey diagram showing the transfer of 100J electrical input energy to 10J useful light energy and 90J wasted heat energy in an electric lamp.

A