physics paper 1

What is energy?

The ability to do work or cause change.

What is the law of conservation of energy?

Energy cannot be created or destroyed, only transferred, stored or dissipated.

What does "dissipated" energy mean?

Energy that is spread out to the surroundings, usually as heat, and becomes less useful.

What are the main energy stores?

Thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic and nuclear.

What is kinetic energy?

The energy an object has because it is moving.

What is the equation for kinetic energy?

KE = 1/2 × m × v²

What do m and v stand for in kinetic energy?

m = mass (kg), v = speed (m/s)

What is gravitational potential energy?

The energy stored by an object raised in a gravitational field.

What is the equation for gravitational potential energy?

GPE = m × g × h

What do m, g and h stand for in GPE?

m = mass (kg), g = gravitational field strength (N/kg), h = height (m)

What is the gravitational field strength on Earth?

About 9.8 N/kg (often rounded to 10 N/kg)

What is elastic potential energy?

Energy stored when an object is stretched or compressed.

What is the equation for elastic potential energy?

EPE = 1/2 × k × e²

What do k and e stand for in elastic potential energy?

k = spring constant (N/m), e = extension (m)

What is specific heat capacity?

The energy needed to raise the temperature of 1 kg of a substance by 1°C.

What is the equation linking thermal energy, mass and temperature change?

ΔE = m × c × ΔT

What does c mean in the specific heat capacity equation?

Specific heat capacity in J/kg°C

What does ΔT mean?

The change in temperature.

How is power defined?

The rate at which energy is transferred.

What is the equation for power?

Power = Energy transferred ÷ Time

What is the unit of power?

Watt (W)

What does 1 watt mean?

1 joule of energy transferred every second.

What is the equation linking efficiency, useful energy output and total energy input?

Efficiency = useful energy output ÷ total energy input

How can efficiency be written as a percentage?

Efficiency = (useful energy output ÷ total energy input) × 100

What is a renewable energy resource?

An energy resource that is replaced naturally and will not run out.

Name 5 renewable energy resources.

Solar, wind, hydroelectric, tidal/wave, geothermal.

Name 3 non-renewable energy resources.

Coal, oil, natural gas, nuclear fuel.

What are the advantages of renewable energy resources?

They won’t run out and usually produce less pollution.

What are the disadvantages of renewable energy resources?

Some are unreliable, expensive to set up, and depend on weather/location.

What are the advantages of fossil fuels?

Reliable, high energy output, useful for transport and electricity generation.

What are the disadvantages of fossil fuels?

They are non-renewable and release greenhouse gases and pollutants.

Why is nuclear fuel classed as non-renewable?

The fuel supply is finite and will eventually run out.

What are the advantages of nuclear power?

Reliable and produces no greenhouse gases while generating electricity.

What are the disadvantages of nuclear power?

Radioactive waste, risk of accidents, and expensive decommissioning.

How does a hydroelectric power station generate electricity?

Water turns turbines which drive generators.

How do wind turbines generate electricity?

Wind turns the blades, spinning a turbine connected to a generator.

How do solar cells generate electricity?

They convert light energy directly into electrical energy.

What is a closed system in energy transfers?

A system where no energy is transferred to or from the surroundings.

What happens to the total energy in a closed system?

It stays constant.

What is work done?

Energy transferred when a force moves an object through a distance.

What is the equation for work done?

Work done = Force × Distance moved in the direction of the force

What is the unit of work done?

Joule (J)

What is electric current?

The rate of flow of electric charge.

What is the unit of current?

Ampere (A)

What is the equation linking charge, current and time?

Q = I × t

What do Q, I and t stand for?

Q = charge (C), I = current (A), t = time (s)

What is potential difference?

The energy transferred per unit charge passing through a component.

What is the unit of potential difference?

Volt (V)

What is the equation linking energy transferred, charge and potential difference?

E = Q × V

What is resistance?

A measure of how difficult it is for current to flow through a component.

What is the unit of resistance?

Ohm (Ω)

What is the equation linking potential difference, current and resistance?

V = I × R

What happens to current if resistance increases and voltage stays the same?

Current decreases.

In a series circuit, what happens to the current?

The current is the same everywhere.

In a series circuit, what happens to the potential difference?

The total potential difference is shared between the components.

In a series circuit, what happens to total resistance?

The total resistance is the sum of all the resistances.

In a parallel circuit, what happens to the potential difference?

The potential difference across each branch is the same as the supply.

In a parallel circuit, what happens to the current?

The total current is split between the branches.

In a parallel circuit, what happens if one branch is removed?

The other branches keep working.

What is the equation for electrical power?

P = I × V

What is the equation for energy transferred electrically?

E = P × t

What is another equation for electrical power using resistance?

P = I²R

What is another equation for electrical power using voltage and resistance?

P = V² ÷ R

What is mains electricity in the UK?

An alternating current supply of about 230 V and 50 Hz.

What does alternating current (AC) mean?

The current repeatedly changes direction.

What does direct current (DC) mean?

The current flows in one direction only.

What type of current is supplied by cells and batteries?

Direct current (DC)

What is the live wire?

The wire in a mains cable that carries the alternating potential difference.

What is the neutral wire?

The wire that completes the circuit and is close to 0 V.

What is the earth wire for?

A safety wire that carries current to ground if there is a fault.

What is a fuse?

A safety device that melts and breaks the circuit if the current gets too large.

What is a circuit breaker?

A safety device that automatically switches off if the current is too high.

Why is a metal case connected to the earth wire?

So that if the live wire touches the case, current flows to earth and the fuse melts.

What is a thermistor?

A resistor whose resistance changes with temperature.

What happens to the resistance of an NTC thermistor when temperature increases?

It decreases.

What is an LDR?

A light-dependent resistor whose resistance changes with light intensity.

What happens to the resistance of an LDR when light intensity increases?

It decreases.

Why are I-V graphs different for a filament lamp?

Its resistance changes because it gets hotter as current increases.

What is an ohmic conductor?

A component that obeys Ohm’s law and has a constant resistance at constant temperature.

What does the I-V graph of a resistor at constant temperature look like?

A straight line through the origin.

What does the I-V graph of a diode show?

It only allows current to flow in one direction once the forward voltage is high enough.

What are the 3 states of matter?

Solid, liquid and gas.

How are particles arranged in a solid?

Closely packed in a fixed, regular arrangement.

How do particles move in a solid?

They vibrate about fixed positions.

How are particles arranged in a liquid?

Close together but in an irregular arrangement.

How do particles move in a liquid?

They move around each other randomly.

How are particles arranged in a gas?

Far apart and randomly arranged.

How do particles move in a gas?

They move quickly in random directions.

What is internal energy?

The total energy stored by the particles in a system.

What happens to particles when a substance is heated?

Their internal energy increases.

What is melting?

The change of state from solid to liquid.

What is boiling?

The change of state from liquid to gas throughout the liquid.

What is evaporation?

The change from liquid to gas at the surface of a liquid.

What is condensing?

The change of state from gas to liquid.

What is freezing?

The change of state from liquid to solid.

What is sublimation?

The change of state directly from solid to gas, or gas to solid.

What is density?

Mass per unit volume.

What is the equation for density?

Density = Mass ÷ Volume