Define useful energy .

Useful energy is an energy transfer that serves an intended purpose .

Define wasted energy .

Wasted energy is an energy transfer that is not useful for the intended purpose and is dissipated to the surroundings.

What is meant by energy being dissipated ?

Energy that is transferred to the surroundings is spread out, or dissipated , and becomes very difficult to use again.

Not all ______ energy is wasted energy, for example the light emitted by a television is a useful transfer.

Not all dissipated energy is wasted energy, for example the light emitted by a television is a useful transfer.

Name three factors that affect how effective an insulator is.

The thermal conductivity , density and thickness of the material.

How does lubricating the moving parts of a machine reduce wasted energy?

Lubrication reduces the friction between moving parts, reducing the energy transferred to the thermal store of the machine and surroundings.

True or False? Energy is "lost" when a machine wastes energy through friction.

False. Energy is dissipated to the surroundings, not lost, because energy is always conserved .

Define thermal conduction .

Thermal conduction is the process where energy is transferred by vibrating particles in a substance, from their kinetic store to the kinetic store of neighbouring particles.

In which direction does energy transfer occur during conduction?

Energy transfers from hot to cold regions.

What is meant by thermal equilibrium ?

Thermal equilibrium is when two objects reach the same temperature , so there is no longer a net transfer of energy between them.

List three factors that affect the rate of energy transfer by conduction.

The thickness of the material, the thermal conductivity of the material, and the temperature difference between the two areas.

The rate of energy transfer by conduction can be reduced by increasing the ______ of the material.

The rate of energy transfer by conduction can be reduced by increasing the thickness of the material.

True or False? Non-metals are generally better thermal conductors than metals.

False. Metals are extremely good thermal conductors, while non-metals, liquids and gases are poor conductors, called insulators .

Efficiency is the ratio of the useful energy output from a system to its total energy input .

What are the units of efficiency?

Efficiency has no units ; it is expressed only as a ratio (0 to 1) or a percentage (0% to 100%).

A system with ______ efficiency wastes most of the energy transferred.

A system with low efficiency wastes most of the energy transferred.

True or False? A device can have an efficiency greater than 100%.

False. Due to conservation of energy , the useful energy output can never exceed the total energy input, so efficiency cannot exceed 100%.

Name four causes of wasted energy in a machine.

Friction between moving parts, air resistance , electrical resistance and noise .

How can friction between moving parts of a machine be reduced?

By adding bearings to prevent components rubbing directly together, or by lubricating the parts.

How can electrical resistance in a circuit be reduced?

By using components with a lower resistance , or by reducing the current .

Why does a racing cyclist adopt a streamlined posture?

To reduce air resistance , which reduces the energy wastefully transferred by heating to the cyclist and surroundings.

Tightening loose parts of machinery reduces vibrations and therefore reduces wasted energy transferred as ______ .

Tightening loose parts of machinery reduces vibrations and therefore reduces wasted energy transferred as sound .

True or False? The efficiency of a device is improved by increasing both the useful and wasted energy transfers.

False. Efficiency is improved by increasing the useful energy transfers and reducing the wasted energy transfers.

Define a renewable energy resource.

A renewable energy resource is one that is replenished at a faster rate than the rate at which it is being used, so it will not run out.

Define a non-renewable energy resource.

A non-renewable energy resource, such as fossil fuels or nuclear fuel, is one that will eventually run out .

What is the energy transfer pathway when a fossil fuel power station generates electricity?

Chemical store of fuel → thermal store of water → kinetic store of turbine → kinetic store of generator → transferred electrically to the National Grid.

What is meant by a reliable energy resource?

A reliable energy resource can produce energy at any time , unlike non-reliable resources such as wind or solar.

In a hydroelectric dam, energy is transferred from the ______ store of the water to the kinetic store of the turbine.

In a hydroelectric dam, energy is transferred from the gravitational potential store of the water to the kinetic store of the turbine.

Name the three main uses of energy resources.

Transport , electricity generation and heating .

True or False? Biofuels are universally accepted as being carbon-neutral.

False. The claim that biofuels are carbon-neutral is largely controversial .

GCSEPhysicsEdexcelFlashcards3. Conservation of EnergyEfficiency & Energy Resources

Efficiency & Energy Resources (Edexcel GCSE Physics): Flashcards

Exam code: 1PH0

1/32

0Still learning

Know0

FrontWasted Energy
Define useful energy.

Was this flashcard helpful?

Cards in this collection (32)

Define useful energy.
Useful energy is an energy transfer that serves an intended purpose.
Define wasted energy.
Wasted energy is an energy transfer that is not useful for the intended purpose and is dissipated to the surroundings.
What is meant by energy being dissipated?
Energy that is transferred to the surroundings is spread out, or dissipated, and becomes very difficult to use again.
Not all ______ energy is wasted energy, for example the light emitted by a television is a useful transfer.
Not all dissipated energy is wasted energy, for example the light emitted by a television is a useful transfer.
Name three factors that affect how effective an insulator is.
The thermal conductivity, density and thickness of the material.
How does lubricating the moving parts of a machine reduce wasted energy?
Lubrication reduces the friction between moving parts, reducing the energy transferred to the thermal store of the machine and surroundings.
True or False?
Energy is "lost" when a machine wastes energy through friction.
False.
Energy is dissipated to the surroundings, not lost, because energy is always conserved.
Define thermal conduction.
Thermal conduction is the process where energy is transferred by vibrating particles in a substance, from their kinetic store to the kinetic store of neighbouring particles.
In which direction does energy transfer occur during conduction?
Energy transfers from hot to cold regions.
What is meant by thermal equilibrium?
Thermal equilibrium is when two objects reach the same temperature, so there is no longer a net transfer of energy between them.
List three factors that affect the rate of energy transfer by conduction.
The thickness of the material, the thermal conductivity of the material, and the temperature difference between the two areas.
The rate of energy transfer by conduction can be reduced by increasing the ______ of the material.
The rate of energy transfer by conduction can be reduced by increasing the thickness of the material.
True or False?
Non-metals are generally better thermal conductors than metals.
False.
Metals are extremely good thermal conductors, while non-metals, liquids and gases are poor conductors, called insulators.
Define efficiency.
Efficiency is the ratio of the useful energy output from a system to its total energy input.
What is the equation for percentage efficiency?
$e f f i c i e n c y = \frac{u s e f u l e n e r g y t r a n s f e r r e d b y t h e d e v i c e}{t o t a l e n e r g y s u p p l i e d t o t h e d e v i c e} \times 100 %$
What are the units of efficiency?
Efficiency has no units; it is expressed only as a ratio (0 to 1) or a percentage (0% to 100%).
A motor is supplied with 300 J of energy, of which 85 J is wasted. Calculate its percentage efficiency.
Useful energy = 300 − 85 = 215 J
$e f f i c i e n c y = \frac{215}{300} \times 100 % = 72 %$
A system with ______ efficiency wastes most of the energy transferred.
A system with low efficiency wastes most of the energy transferred.
True or False?
A device can have an efficiency greater than 100%.
False.
Due to conservation of energy, the useful energy output can never exceed the total energy input, so efficiency cannot exceed 100%.
Name four causes of wasted energy in a machine.
Friction between moving parts, air resistance, electrical resistance and noise.
How can friction between moving parts of a machine be reduced?
By adding bearings to prevent components rubbing directly together, or by lubricating the parts.
How can electrical resistance in a circuit be reduced?
By using components with a lower resistance, or by reducing the current.
Why does a racing cyclist adopt a streamlined posture?
To reduce air resistance, which reduces the energy wastefully transferred by heating to the cyclist and surroundings.
Tightening loose parts of machinery reduces vibrations and therefore reduces wasted energy transferred as ______.
Tightening loose parts of machinery reduces vibrations and therefore reduces wasted energy transferred as sound.
True or False?
The efficiency of a device is improved by increasing both the useful and wasted energy transfers.
False.
Efficiency is improved by increasing the useful energy transfers and reducing the wasted energy transfers.
Define a renewable energy resource.
A renewable energy resource is one that is replenished at a faster rate than the rate at which it is being used, so it will not run out.
Define a non-renewable energy resource.
A non-renewable energy resource, such as fossil fuels or nuclear fuel, is one that will eventually run out.
What is the energy transfer pathway when a fossil fuel power station generates electricity?
Chemical store of fuel → thermal store of water → kinetic store of turbine → kinetic store of generator → transferred electrically to the National Grid.
What is meant by a reliable energy resource?
A reliable energy resource can produce energy at any time, unlike non-reliable resources such as wind or solar.
In a hydroelectric dam, energy is transferred from the ______ store of the water to the kinetic store of the turbine.
In a hydroelectric dam, energy is transferred from the gravitational potential store of the water to the kinetic store of the turbine.
Name the three main uses of energy resources.
Transport, electricity generation and heating.
True or False?
Biofuels are universally accepted as being carbon-neutral.
False.
The claim that biofuels are carbon-neutral is largely controversial.

Sign up to unlock flashcards

By signing up you agree to our Terms and Privacy Policy

Previous:Conservation of EnergyNext:Properties of Waves