Efficiency of Machines Flashcards

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1
Q

Why do we call it wasted heat?

A

Because we can’t do anything useful with it.

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2
Q

What is useful energy?

A

Concentrated energy.

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3
Q

The entire energy output by a machine both useful and wasted, ends up as what?

A

Heat.

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4
Q

Where is the heat transferred to?

A

Cooler surroundings, which then becomes warmer.

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5
Q

What happens when the heat is transferred to cooler surroundings?

A

The energy becomes less concentrated.

It dissipates.

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6
Q

What happens the energy?

A

The total amount stays the same.

It just becomes increasingly spread out.

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7
Q

The spread out energy can not be what?

A

Easily used or collected back in again.

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8
Q

What do you need to think about when choosing appliances?

A

The cost-effectiveness and efficiency.

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9
Q

EXAMPLE.

A low-energy bulb is what?

A

About 4 times as efficient as an ordinary light bulb.

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10
Q

EXAMPLE.

What is a energy-efficient light bulb?

A

A more expensive light bulb that lasts longer.

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11
Q

EXAMPLE.

If an energy-saving light bulb was £3 and saved £12 a year, what would be it’s payback time?

A

3 months.

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12
Q

EXAMPLE.

Compare energy saving light bulbs and ordinary light bulbs?

A

More efficient than low-energy light bulbs.

Last longer.

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13
Q

EXAMPLE.

Disadvantage of energy-saving light bulbs?

A

Expensive.

Don’t give out as much light as the other two types of bulb.

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14
Q

New, efficient appliances are what?

A

Cheaper to run than old, less efficient appliances.

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15
Q

How do you work out the cost-effectiveness of a new appliance?

A

Need to work out its payback time.

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16
Q

Sometimes what can ‘waste’ energy be?

A

Actually useful.

17
Q

What do heat exchangers do?

A

Reduce the amount of heat energy that is ‘lost’.

18
Q

How do heat exchangers reduce the amount of heat energy that is lost?

A

By pumping a cool fluid through the escaping heat.

19
Q

What happens to the temperature of this fluid?

A

Rises as it gains heat energy.

20
Q

The heat energy in the fluid can be then what?

A

Converted into a form of energy that’s useful again.

Either in the original energy or other useful functions.

21
Q

EXAMPLE.

Heat from the car’s engine can be transferred to what?

A

The air to warm up passenger compartment.