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What is meant by the conservation of energy?
Energy cannot be created or destroyed, only transferred, stored, or dissipated.
What is meant by 'dissipation' of energy?
Energy becoming spread out and stored in less useful ways, often as thermal energy.
What is the definition of specific heat capacity?
The amount of energy required to raise the temperature of 1 kg of a substance by 1°C.
Why are metals good conductors of heat?
They contain free electrons that transfer energy quickly through the material.
What reduces energy transfer by conduction?
Using insulating materials with low thermal conductivity.
How can energy transfers be reduced in homes?
Loft insulation
cavity wall insulation
double glazing
thick curtains
What does the national grid do?
Transfers electrical power from power stations to consumers across the country.
Why is electricity transferred at high voltage?
To reduce current, which reduces energy lost as heat in cables.
What is a renewable energy source?
One that can be replenished naturally and won’t run out.
Name 3 renewable energy sources.
Solar, wind, hydroelectric.
Name 3 non-renewable energy sources.
Coal, oil, natural gas.
What are the environmental impacts of burning fossil fuels?
Releases CO2 (causing climate change) and sulfur dioxide (causing acid rain).
What is an electric current?
The flow of electric charge (electrons) through a conductor.
What is resistance?
The opposition to the flow of current in a circuit.
What is Ohmic behaviour?
When current through a component is directly proportional to voltage across it (constant resistance).
What happens to resistance in a filament lamp as temperature increases?
It increases
so current does not increase proportionally.
What is the function of a diode?
Allows current to flow in only one direction.
What is the function of an LDR?
Its resistance decreases as light intensity increases.
What is the function of a thermistor?
Its resistance decreases as temperature increases.
What is the difference between series and parallel circuits?
In series, current is the same everywhere
in parallel, voltage is the same across branches
What is the UK mains voltage and frequency?
230 V and 50 Hz.
What are the three wires in a plug and their colours?
Live (brown), neutral (blue), earth (green/yellow).
Why is the earth wire important?
It carries current away if there is a fault
and prevents electric shock.
What happens if the live wire touches a metal case?
The case becomes live and could cause electric shock unless earthed.
What is the function of a fuse?
It melts and breaks the circuit if the current is too high.
What is internal energy?
The total kinetic and potential energy of particles in a substance.
What happens to internal energy when a substance is heated?
It increases.
What causes a change of state?
Energy being added or removed, changing the internal energy without changing temperature.
What is the process of melting?
Solid to liquid.
What is the process of condensation?
Gas to liquid.
What is the process of sublimation?
Solid to gas.
What is the particle model of matter?
Model where substances are made of tiny particles in constant motion.
What is density?
Mass per unit volume of a substance.
How does temperature affect particle motion?
Higher temperature = particles move faster.
What is meant by specific latent heat?
Energy needed to change the state of 1 kg of a substance without a temperature change.
What did the alpha particle experiment show?
Most of the atom is empty space, with a dense, positive nucleus.
What are the charges and relative masses of protons, neutrons and electrons?
Proton: +1, mass 1
Neutron: 0, mass 1
Electron: -1, mass ≈ 0.
What is an isotope?
Atoms of the same element with different numbers of neutrons.
What is radioactive decay?
When an unstable nucleus releases radiation to become more stable.
What is ionising radiation?
Radiation that knocks electrons off atoms, forming ions.
What are the three types of nuclear radiation?
Alpha, beta, gamma.
What is alpha radiation?
2 protons and 2 neutrons (helium nucleus), highly ionising, low penetration.
What is beta radiation?
A fast-moving electron
moderately ionising
medium penetration.
What is gamma radiation?
Electromagnetic wave
weakly ionising
highly penetrating.
What stops alpha radiation?
A sheet of paper or a few cm of air.
What stops beta radiation?
A few mm of aluminium.
What stops gamma radiation?
Several cm of lead or meters of concrete.
What is the half-life of a radioactive substance?
Time taken for the number of radioactive nuclei to halve.
Why is half-life useful?
It helps determine the age of objects
or how long a substance remains dangerous.
What are the dangers of ionising radiation?
It can damage cells and DNA, potentially causing cancer.
How can radiation be used in medicine?
In tracers (diagnostic) or to treat cancer (radiotherapy).