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Efficiency Calculations

Last updated almost 5 years ago
23 questions
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1

Energy cannot be...

1

When a lightbulb warms up what is the wasted energy?

1

How could you reduce the amount of air resistance acting on an object?

1

Which equipment would you use to measure 93ml of water?

1

A child runs 1200m in 260 seconds. What is their speed?

1

Challenge: name the 8 energy stores.

Key Knowledge: LCWC
1

Define Efficiency

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State the equation used to calculate efficiency

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Name the two ways efficiency can be written

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Name the energy transferred to the surroundings

Recall Quiz
1

What is the correct definition of efficiency?

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State the equation used to calculate efficiency

1

If a kettle has an efficiency of 0.875, what is this efficiency written as a percentage?

1

When energy has been transferred to the surroundings it has…

I do
1

400 Joules of energy goes in and 350 Joules is transferred to thermal energy therefore only ………….. Joules of sound is wasted

You do
1

10,000 Joules of kinetic energy goes in and 8,000 Joules of energy is transferred to electrical and therefore only ……………Joules of heat energy is dissipated.

I Do
1

Calculate the efficiency, as a percentage, of a speaker that uses 300 J which it radiates as 96 J of sound energy.

We Do
1

100J of energy is transferred electrically to a filament bulb, of which 45J are radiated usefully as light. Calculate its efficiency as a percentage.

You Do
1

250J of energy is transferred electrically to a filament bulb, of which 150J are radiated as light and 100J stored thermally in the filament. Calculate its efficiency as a percentage.

Challenge
1

2.5kJ of energy is transferred electrically to a filament bulb. The efficiency of the lamp is 0.4. Calculate how much energy is usefully transferred

Plenary
1

To calculate efficiency you divide ________ by __________.

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If an energy transfer is very efficient that means that a (large/small) amount of energy is being transferred usefully & a (large/small) amount is dissipated.

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3)If a transfer has an efficiency of 0.75, we can also write this as being ___________% efficient.