Energy Work and Power IGCSE

A solar panel is used to recharge a battery. The solar panel produces 0.80 W of electrical power.

The panel is 20% efficient.

What is the power input of the sunlight onto the solar panel?

• 0.16 W

• 4.0 W

• 8.0 W

• 16 W

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The diagrams show four different athletes training by doing pull-ups.

Which athlete does the most work?

• 
• 
• 
• 

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A motor is used to lift a load of 40 N.

The power of the motor is 40 W and the system is 20% efficient.

How long does it take the motor to lift the load through 0.50 m?

• 0.50 s

• 2.5 s

• 5.0 s

• 25 s

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The diagrams show athletes training by stretching springs.

Each spring has the same stiffness.

Which athlete does the most work?

• 
• 
• 
• 

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NGSS.MS-PS3-5

An electric generator produces an electromotive force (e.m.f.) of 200 V and produces a current of 3.0 A in a circuit.

The generator is driven by an engine with a power of 2.4 kW.

What is the efficiency of the generator?

• 2.8%

• 25%

• 28%

• 36%

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Different processes have different efficiencies.

Which row shows the most efficient process?

• A

• B

• C

• D

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A 150 W filament lamp has an efficiency of 10%. A 40 W compact fluorescent lamp (CFL) has an

efficiency of 30%.

Each lamp is switched on for the same amount of time.

Which lamp produces more light and which lamp converts more energy into other forms of

energy

• A

• B

• C

• D

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NGSS.MS-ETS1-2

A lamp has a power input of 5.0 W. It wastes 1.0 W of power heating the surroundings.

What is the efficiency of the lamp?

• 20%

• 50%

• 80%

• 120%

A car of mass 800 kg travels over a hill of height h.

By travelling to the top of the hill, the car gains 40000 J of gravitational potential energy.

The gravitational field strength g is 10 N /kg.

What is the height h of the hill?

• 5.0 m

• 20 m

• 50 m

• 500 m

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NGSS.MS-PS2-4

A pendulum bob swings along the path WXYZ and back again. Resistive forces can be ignored.

Which statement describes the total energy of the bob?

• It has a maximum value at X.

• It has a maximum value at Y

• It has a maximum value at Z

• It has the same value at W, X, Y and Z

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