Physics Paper 1 & 2 – Key Concepts Review

Flashcards cover conservation of energy, energy transfers, efficiency, National Grid, power stations, household insulation, basic electricity, circuit rules, molecules & matter, radioactivity, and key physics equations/units.

What happens to the energy stores of the wood, pipe and water when water is heated over a wood fire?

Chemical store of the wood decreases; thermal store of the pipe increases; thermal store of the water increases.

In a bat hitting a ball, which energy store does the bat initially possess?

Kinetic energy store.

During a bat–ball collision, how is energy usefully transferred to the ball?

Mechanically to the ball’s kinetic store.

Name one way energy is dissipated when a bat hits a ball.

Heating of the bat, ball and surrounding air.

While a boy is airborne on a trampoline, which two energy stores alternate?

Kinetic store of the boy and elastic potential store of the trampoline.

As the boy on a trampoline rises, which energy store increases?

Gravitational potential store of the boy.

State the useful energy transfer in a battery-powered toy car.

Electrical transfer from the battery’s chemical store to the car’s kinetic store.

What main energy transfer occurs when a falling apple hits the ground?

Kinetic store of the apple to thermal store of surroundings (via sound).

What is the useful transfer when a stretched elastic band fires a ball?

Mechanical transfer from the elastic potential store of the band to the kinetic store of the ball.

Describe the energy pathway in an electric kettle heating water.

Electrical energy to the element’s thermal store, then heating to the water’s thermal store.

When a moving car slows with brakes, where is most kinetic energy transferred?

Thermal store of the brakes (and surroundings).

List the four ways energy can be transferred.

Mechanically (by forces), electrically, by heating, by radiation/waves.

How does lubrication reduce unwanted energy transfer?

It decreases friction so less energy is dissipated as heat.

Why does streamlining improve efficiency?

Reduces energy wasted to air resistance or drag in water.

Give one form of thermal insulation for a house wall and the process it limits.

Cavity wall insulation with foam limits convection in the cavity.

What happens to energy in a car crash with a stationary object?

Car’s kinetic energy transfers to thermal stores of both car and object and to sound waves.

Explain how thick walls with low thermal conductivity reduce energy loss.

They lower the rate of energy transfer by conduction.

How do cavity walls reduce conduction?

The air gap is an insulator that slows energy transfer by conduction.

How can radiator efficiency be improved inside a room?

Place metal foil behind the radiator to reflect infrared radiation back into the room.

Briefly describe how hydroelectric (pumped-storage) power generates electricity.

Stored water behind a dam flows to turn a turbine, which turns a generator to produce electricity.

State one environmental disadvantage of biofuels.

Burning or decay releases CO₂.

Why is a vacuum better than dry air in double glazing?

Vacuum prevents both conduction and convection; air only reduces conduction.

Name the three factors that determine rate of energy transfer through an insulating layer.

Temperature difference, thickness, thermal conductivity.

Give one advantage and one disadvantage of nuclear power.

Advantage: large energy from small fuel mass. Disadvantage: produces long-lived radioactive waste.

State one environmental impact of burning fossil fuels.

Emission of CO₂ leading to global warming.

Where are step-up transformers placed in the National Grid and what is their purpose?

Between power stations and transmission cables; they increase potential difference.

Why are step-down transformers used before electricity enters homes?

To lower potential difference to safer domestic levels (≈230 V).

Explain why electricity is transmitted at high potential differences.

High PD gives low current, so less energy is lost as heat, making transmission more efficient.

Outline the steps to measure the specific heat capacity of vegetable oil.

Measure oil mass; record start temp; supply electrical energy with heater; record final temp; read energy from joulemeter; use E=mcΔθ to calculate c.

How does a solar cell generate electricity?

Light knocks electrons free in silicon, creating a DC current.

Give one advantage and one disadvantage of solar power stations.

Advantage: no fuel costs. Disadvantage: not reliable (depends on sunlight).

Describe how geothermal power stations generate electricity.

Hot rocks heat water to steam; steam drives turbines and generators.

State one drawback of geothermal power.

Sites are geographically limited and drilling is expensive.

Summarise how tidal power stations operate.

High tide water trapped behind a barrage; released water drives turbines connected to generators.

Name one environmental disadvantage of tidal barrages.

They can destroy habitats of coastal plants and animals.

List two home features that reduce energy transfer by convection.

Loft insulation and draught excluders.

What circuit configuration must an ammeter always use?

Series with the component.

Define potential difference (voltage).

Energy per coulomb transferred between two points in a circuit; 1 V = 1 J/C.

State the equation linking voltage, current and resistance.

V = I × R (or R = V ÷ I).

Give Ohm’s law in words.

At constant temperature, current through an ohmic conductor is directly proportional to potential difference.

In proving Ohm’s law, why is a variable resistor used?

To change the potential difference across the fixed resistor and hence vary current.

Describe the I-V characteristic of an ohmic conductor.

Straight line through the origin, indicating proportionality of I and V.

Why does resistance of a filament lamp increase with temperature?

Electrons and vibrating ions collide more often, impeding current flow.

In a series circuit, how is total resistance calculated?

It equals the sum of individual resistances: R_total = R1 + R2 + R3 …

In a parallel circuit, what happens to the total current?

It equals the sum of branch currents: I = I1 + I2 + …

State the frequency and peak potential of UK mains electricity.

50 Hz, peaks at ±325 V with an RMS value of 230 V.

Give one reason brass is used for plug pins.

It is hard and does not oxidise, yet conducts electricity.

Why is touching a live wire dangerous?

Body at 0 V forms a large potential difference with live wire (≈230 V), causing a current through the body.

Which current equation helps you choose the correct fuse rating?

I = P ÷ V.

Why are appliances earthed?

So fault current flows through low-resistance earth wire instead of the user, preventing electric shock.

Briefly describe the kinetic particle model of a solid.

Particles close and fixed in position, vibrate about fixed points, least energy.

What happens to gas pressure as temperature increases?

Average kinetic energy rises, particles collide more forcefully and often, increasing pressure.

How do you find the density of an irregular solid?

Mass by balance, volume by water displacement, then density = mass/volume.

State two reasons peer review is important in science.

Allows other scientists to check findings and improve validity.

During melting on a heating curve, why does temperature stay constant?

Energy is used to break intermolecular bonds, raising potential energy, not kinetic energy.

Explain how to measure the density of a liquid.

Record mass of empty beaker; measure volume of liquid; find mass of liquid by difference; calculate density = mass/volume.

Why does gas pressure fall when temperature decreases?

Particles have less kinetic energy, collide less often and with less force on container walls.

Define radioactivity.

Spontaneous decay of unstable nuclei emitting radiation until stability is reached.

What is an isotope?

Atoms of the same element with the same proton number but different neutron numbers.

State one property of alpha radiation.

Highly ionising but low penetration; stopped by paper or a few cm of air.

During alpha decay, how do mass and atomic numbers change?

Mass number –4, atomic number –2.

How do mass and atomic numbers change in beta decay?

Mass number stays the same; atomic number increases by 1.

What changes occur during gamma emission?

No change in mass or atomic numbers; nucleus just loses excess energy.

Define half-life.

Time required for half the nuclei in a sample to decay.

Which instrument measures radioactivity and what unit is used?

Geiger–Müller counter; becquerel (Bq) or counts per second/minute.

Differentiate contamination and irradiation.

Irradiation: exposure to radiation. Contamination: unwanted radioactive material on/in an object.

Why is alpha radiation especially dangerous inside the body?

It is highly ionising and causes severe cell damage over short ranges.

Give two safety precautions when handling radioactive sources.

Use long tongs and wear protective gloves (others: lead shielding, minimize exposure time).

How do smoke alarms use alpha radiation?

Alpha particles ionise air, creating a current; smoke absorbs alpha, reducing current and triggering alarm.

How is beta radiation used in thickness control of foil?

Beta count falls if foil thickens; feedback system adjusts roller pressure to maintain set thickness.

Why does a high PD in the National Grid reduce energy losses?

It allows lower current for the same power, so I²R heat losses are smaller.

State the equation for power in terms of current and potential difference.

P = I × V.

What is meant by specific heat capacity?

Energy required to raise the temperature of 1 kg of a substance by 1 °C.

Define specific latent heat.

Energy required to change state of 1 kg of a substance without temperature change.

Write the momentum equation (higher tier).

p = m × v.

What is the unit of magnetic flux density?

Tesla (T).

Give the symbol and unit for electric charge.

Q, coulomb (C).

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

E = Q × V.

State the formula for efficiency as a decimal.

Efficiency = useful energy out ÷ total energy in.

How does loft insulation reduce energy loss by convection?

It traps air layers, preventing convection currents in the loft space.

What is the purpose of draught excluders?

They block gaps around doors/windows to stop convection of warm air out of the house.

In a plug, which colour is the live wire?

Brown.

Which wire in a plug is connected to the longest pin?

Earth wire (green and yellow).

State one key rule for voltmeter connections.

Voltmeter must be connected in parallel with the component being measured.

What is the SI unit of power?

Watt (W).

Write the equation linking force, moment and perpendicular distance.

Moment = force × perpendicular distance from pivot.

Give the unit for pressure.

Pascal (Pa).

Explain why thick glass double glazing reduces energy transfer mainly by conduction.

Glass and trapped air/vacuum are poor conductors, so heat flow through the window is slowed.

Why does air trapped in cavity wall insulation reduce convection?

Small air pockets limit large-scale air movement, suppressing convection currents.

Which property of an insulating material lowers its thermal conductivity?

Presence of trapped air or vacuum and low-conductivity solid structure.