State what is meant by a closed system.

It is a system in which no energy is transferred into or out of the system.

State the net change in the total energy of a closed system when energy is transferred within it.

There is no net change; the total energy stays the same.

A sealed vacuum flask holds hot water and a cold metal block. Describe the energy transfer and state the total energy afterwards.

Energy is transferred from the thermal store of the water to the thermal store of the block until they reach the same temperature, and the total energy is unchanged.

State what is meant by dissipated energy.

It is energy that has been transferred to less useful stores, usually the thermal stores of the surroundings.

AQA GCSE Combined Science Physics 8464

Atomic Structure

Topic overview The structure of an atom Mass number, atomic number and isotopes From the plum pudding model to the nuclear model Chadwick, the neutron, and comparing the models Radioactive decay and nuclear radiation Nuclear equations Half-lives and the random nature of radioactive decay Radioactive contamination

Electricity

Topic overview Circuit symbols, electrical charge and current Current, resistance and potential difference Ohmic conductors, filament lamps, diodes and thermistors Light-dependent resistors, and investigating resistance Current and potential difference in series and parallel Constructing circuits, and calculating in series circuits Direct and alternating potential difference, and mains electricity Power and efficiency Appliances, and the energy transferred by electrical work Power, and the power ratings of domestic appliances The National Grid

Energy

Topic overview Energy stores and systems Kinetic energy Elastic and gravitational potential energy Energy changes in systems Power Energy transfers in a system The main energy resources, renewable and non-renewable Environmental impact and trends in energy use

Forces

Topic overview Scalars, vectors, forces and the resultant force Gravity Work done and energy transfer Stretching, compressing, and the spring constant Linear and non-linear extension, and work done on a spring Resolving forces and free body diagrams Distance, displacement and speed The speed of sound, and the distance-speed-time equation Velocity and the distance-time relationship Acceleration, deceleration and velocity-time graphs Area under a velocity-time graph, and the uniform acceleration equation Newton's First Law Newton's Second and Third Laws Stopping distance and reaction time Factors affecting braking distance Braking force, deceleration and the dangers of stopping quickly Momentum and its conservation

Magnetism and Electromagnetism

Topic overview Poles of a magnet Magnetic fields around a magnet The compass, and plotting a magnetic field Electromagnetism Fleming's left-hand rule and electric motors Transformer power, and using the transformer equations

Particle Model of Matter

Topic overview Density of materials Changes of state and internal energy Temperature changes in a system and specific heat capacity Changes of state and specific latent heat Particle motion in gases

Waves

Topic overview Transverse and longitudinal waves, and the wave equation Wave properties, and refraction at a boundary Types and uses of electromagnetic waves Radio waves, and the hazards of ultraviolet, X-rays and gamma rays

Energy

Energy transfers in a system

3 things to know
Physics Paper 1

Overview

Conservation of energy and closed systems, dissipated energy and why it is wasted, reducing unwanted transfers with lubrication and thermal insulation, how thermal conductivity and wall thickness affect how quickly a building cools, and what is being compared when different materials are wrapped around beakers of hot water.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Explain how lubrication and insulation cut unwanted energy transfers, and what thermal conductivity says about the rate of conduction.

Key term

State whether energy can be created or destroyed, and name the three things that can happen to it instead.

Key term

A device is said to use up energy. Correct this statement.

Questions from this subtopic

Each one with the model answer underneath.

1
State whether energy can be created or destroyed, and name the three things that can happen to it instead.
Model answer
Energy cannot be created or destroyed; it can be transferred usefully, stored, or dissipated.
2
A device is said to use up energy. Correct this statement.
Model answer
Energy is not used up; it is transferred to other stores, some usefully and some dissipated to the surroundings.
3
State what is meant by a closed system.
Model answer
It is a system in which no energy is transferred into or out of the system.
4
State the net change in the total energy of a closed system when energy is transferred within it.
Model answer
There is no net change; the total energy stays the same.
5
A sealed vacuum flask holds hot water and a cold metal block. Describe the energy transfer and state the total energy afterwards.
Model answer
Energy is transferred from the thermal store of the water to the thermal store of the block until they reach the same temperature, and the total energy is unchanged.
6
State what is meant by dissipated energy.
Model answer
It is energy that has been transferred to less useful stores, usually the thermal stores of the surroundings.

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