efficiency form 4

8/8/2019 efficiency form 4

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2.11 The Importance of Maximisingthe Efficiency of Devices.


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Efficiency

Energy convertors change energy from one

from to another.

The energy supplied to the energy convertor isthe input energy

The output energy can be classified into two

types:

(i)the useful energy

(ii)the unwanted energy


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Which one have a higher efficiency?


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The fluorescent bulb is said to have a higher

efficiency than the filament bulb.

Because: The fluorescent bulb converts ahigher percentage of the input energy to the

useful from of energy.


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Maximising Efficiency

The efficiency of energy converters is alwaysless than 100 %

Since the energy resources in this world arelimited, there is a need to maximise theefficiency of devices


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Maximising Efficiency

When a device is operating at the maximumpossible efficiency:

- Less input energy is required to produce

the same useful output energy.- The cost of operating the device is

reduced.

- The unwanted output energy (which may

be harmful to the environment) is reduced.- the energy resources in this world can beused over a longer period of time.


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Example 1: Maximising Efficiency of a

Car


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Energy conversions in the operation of a car.


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Maximising Efficiency of a Car

to reduce friction and heat which is

generated in the engine.Use a good quality lubricant in the

engine

so that excessive sound is reduced.Improve the design of the engine

to reduce air resistance.The body of the car is well streamlined

to reduce resistance to the motion of the

car.The wheels are properly aligned

The bearings at the wheels are in good condition

and all moving parts are well lubricated.

to reduce friction with the road surface.The tyres are inflated to the correct

pressure


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Example 2: Maximising Efficiency of a

Table fan


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Energy conversions in the operation of

a table fan


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Maximising Efficiency of a Table fan

to reduce friction.The bearings of the motor are

in good condition

to reduce the energy lost as heat.The wires in the coil of the

motor have low resistance

there will be no vibrations that willproduce unnecessary sound..

The parts of the fan are

joined securely

so that they rotate smoothly.

The blades of the fan are

well balanced

where there is no strong winds thatcould oppose the rotation of theblades.

The fan is not placed near

doors or windows


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Spice Up Your Mind.

Figure above shows a cyclist in a race. He needs to maximise

efficiency so that more of his input energy becomes kinetic

energy.

Study figure above and list the ways efficiency are

maximised.


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Air resistance is minimised by:

- bending his body to a crouched

position

- wearing figure hugging shirt and thepants made of smooth material

- Wearing helmet that has a streamlinedshape

A design of chain and gears so that ahigher percentage of work done by thecyclist becomes kinetic energy.


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efficiency form 4

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