AQA GCSE Physics Required Practicals

Aim

Measure how much energy is needed to raise the temperature of 1 kg of a material by 1 °C.

Method

1. Measure the mass of the block with a balance.
2. Insulate the block and place a heater in the larger hole and a thermometer in the smaller hole, using a little oil or water for good thermal contact.
3. Connect the heater to a power supply through an ammeter, with a voltmeter across the heater, and record the starting temperature.
4. Switch on and start the stopwatch, recording current and potential difference.
5. Record the temperature at regular intervals, for example every minute, for around 10 minutes.
6. Calculate the energy supplied and plot temperature against energy.

Variables

Equipment

Metal block with holes, Immersion heater, Thermometer, Power supply, Ammeter and voltmeter, Balance, Stopwatch, Insulation.

Results and observations

Temperature rises steadily as energy is supplied. Different materials of the same mass reach different temperatures for the same energy input.

Calculations

• E = P × t, and P = V × I, so energy supplied E = V × I × t
• ΔE = m × c × Δθ, so c = ΔE ÷ (m × Δθ)
• Mass must be in kilograms and temperature change in °C

Graphs and data

Plot temperature (y) against energy supplied (x); the specific heat capacity is 1 ÷ (gradient × mass).

Evaluation

• Energy lost to the surroundings makes the measured specific heat capacity higher than the true value, so insulation is important.
• The thermometer measures the block near the surface, which may lag behind the average temperature.
• Oil in the thermometer hole improves thermal contact and reduces the lag.
• Not all electrical energy heats the block; some warms the heater and the surroundings.

Common mistakes

• Using mass in grams instead of kilograms.
• Using the final temperature instead of the temperature change.
• Forgetting that the heater needs time before the temperature responds.

Quick self-test

Linked topic: Energy revision

Aim

Compare how well different materials, or different thicknesses of a material, reduce the rate of cooling.

Method

1. Wrap an identical beaker in each insulating material, keeping the number of layers consistent within a run.
2. Pour the same volume of hot water at the same starting temperature into each beaker.
3. Fit a lid with a thermometer through it to reduce evaporation.
4. Record the temperature every minute for around 10 minutes.
5. Repeat with the other materials, and with different thicknesses of one material.
6. Compare temperature drops over the same time interval.

Variables

Equipment

Identical beakers, Insulating materials, Thermometer or temperature probe, Lids, Measuring cylinder, Stopwatch, Kettle.

Results and observations

Better insulators show a smaller temperature drop over the same time. Adding layers reduces the drop further, with diminishing returns.

Calculations

• Temperature drop = starting temperature − final temperature
• Mean rate of cooling = temperature drop ÷ time (°C per minute)

Graphs and data

Plot temperature against time for each material on the same axes; the shallowest curve is the best insulator.

Evaluation

• Using the same volume and starting temperature makes the comparison fair, since more water cools more slowly.
• Lids are needed because evaporation causes cooling independently of the insulation.
• Room temperature drifting between runs affects the rate of cooling.
• Repeats give a mean and reduce the effect of random variation.

Common mistakes

• Comparing final temperatures when the starting temperatures were different.
• Varying the thickness and material at the same time.
• Leaving beakers uncovered so evaporation dominates.

Quick self-test

Aim

Find how the length of a wire affects its resistance, and how resistance changes for resistors in series and parallel.

Method

1. Set up a circuit with a power supply, ammeter in series and a voltmeter in parallel across the test wire.
2. Attach crocodile clips to the wire so that a measured length is in the circuit.
3. Close the switch briefly, record current and potential difference, then open it again to avoid heating the wire.
4. Repeat for a range of lengths, for example 10 cm to 100 cm.
5. For the resistor part, measure current and potential difference for one resistor, then for two in series, then two in parallel.
6. Calculate resistance for each arrangement using R = V ÷ I.

Variables

Equipment

Power supply, Ammeter and voltmeter, Resistance wire on a metre rule, Crocodile clips, Switch, Fixed resistors, Leads.

Results and observations

Resistance is directly proportional to length for a wire at constant temperature. Resistors in series give a total resistance equal to the sum; resistors in parallel give a total less than the smallest individual resistance.

Calculations

• R = V ÷ I
• Series: R_total = R₁ + R₂
• Parallel: the total resistance is smaller than either individual resistance

Graphs and data

Plot resistance (y) against length (x); a straight line through the origin shows direct proportionality.

Evaluation

• Current heats the wire, which raises its resistance, so the switch is kept closed only briefly.
• Crocodile clip position must be read carefully against the ruler; parallax causes systematic error.
• Contact resistance at the clips adds a small constant error.
• Repeats at each length allow a mean resistance.

Common mistakes

• Leaving the circuit switched on so the wire heats up and results drift.
• Connecting the voltmeter in series rather than in parallel.
• Assuming parallel resistance is the sum, rather than less than the smallest resistor.

Quick self-test

Linked topic: Electricity revision

Aim

Show how current varies with potential difference for different circuit components.

Method

1. Build a series circuit with the component, an ammeter and a variable resistor, with a voltmeter across the component.
2. Adjust the variable resistor to change the potential difference in steps.
3. Record current and potential difference at each step.
4. Reverse the connections to the power supply and repeat to get negative values.
5. Repeat for the resistor, the filament lamp and the diode.
6. For the diode, add a protective resistor in series to limit the current.

Variables

Equipment

Power supply, Ammeter and voltmeter, Variable resistor, Fixed resistor, filament lamp and diode, Protective resistor, Leads and switch.

Results and observations

A resistor at constant temperature gives a straight line through the origin. A filament lamp gives an S-shaped curve that flattens as it heats up. A diode conducts in one direction only, with almost no current in reverse.

Calculations

• R = V ÷ I at any point on the graph
• For the ohmic resistor, resistance is the reciprocal of the gradient of I against V

Graphs and data

Plot current (y) against potential difference (x), including negative values, so the shape either side of the origin is visible.

Evaluation

• The filament lamp's resistance rises because the metal filament gets hotter, so the graph curves.
• Taking readings quickly keeps the resistor near constant temperature so its line stays straight.
• A protective resistor prevents a large current damaging the diode when forward biased.
• Repeats and reversed readings check for symmetry and expose anomalies.

Common mistakes

• Plotting potential difference on the y-axis when the question specifies I–V.
• Saying the lamp is ohmic because part of the graph looks straight.
• Omitting the protective resistor with the diode.

Quick self-test

Linked topic: Electricity revision

Aim

Determine density from measurements of mass and volume for solids and liquids.

Method

1. Regular solid: measure mass on a balance, then measure the dimensions with a ruler or vernier callipers and calculate the volume.
2. Irregular solid: measure the mass, then lower the object into a eureka can filled to the spout and collect the displaced water in a measuring cylinder.
3. The volume of displaced water equals the volume of the object.
4. Liquid: measure the mass of an empty measuring cylinder, add a known volume of liquid, then reweigh.
5. Subtract to find the mass of the liquid.
6. Calculate density in each case and repeat measurements to find means.

Variables

Equipment

Balance, Ruler or vernier callipers, Eureka (displacement) can, Measuring cylinder, Beaker, Objects and liquids to test.

Results and observations

Density values allow materials to be identified and compared; objects less dense than water float, which affects how they must be submerged.

Calculations

• ρ = m ÷ V, with mass in kg and volume in m³ for kg/m³, or g and cm³ for g/cm³
• Volume of a cuboid = length × width × height
• 1 cm³ of displaced water = 1 cm³ of object volume

Graphs and data

For a liquid, plot mass against volume; the gradient is the density.

Evaluation

• A floating object must be pushed fully under with a thin rod, or the volume is underestimated.
• Water left clinging to the object or lost as splashes gives a systematic error in the displaced volume.
• A measuring cylinder has lower resolution than a burette, and the meniscus must be read at eye level.
• Vernier callipers give a more precise dimension measurement than a ruler.

Common mistakes

• Mixing units, for example mass in grams with volume in m³.
• Reading the measuring cylinder from above, causing parallax error.
• Forgetting to subtract the mass of the empty container when finding a liquid's mass.

Quick self-test

Aim

Show how the extension of a spring changes with the force applied, and find its spring constant.

Method

1. Clamp the spring securely to a stand with a ruler fixed vertically alongside it.
2. Record the unstretched length of the spring.
3. Add a known mass to the hanger and record the new length once it is still.
4. Repeat, adding masses one at a time and recording the length each time.
5. Remove the masses one at a time, checking the spring returns to its original length.
6. Calculate the extension for each force and plot a graph.

Variables

Equipment

Spring, Clamp stand, boss and clamp, Ruler and set square, Slotted masses and hanger, Safety goggles and floor mat.

Results and observations

Extension is directly proportional to force up to the limit of proportionality. Beyond that the line curves and the spring may not return to its original length.

Calculations

• Weight: W = m × g, with g = 9.8 N/kg
• Extension = stretched length − original length
• F = k × e, so the spring constant k = force ÷ extension (N/m)

Graphs and data

Plot force (y) against extension (x); the straight section passes through the origin and its gradient is the spring constant.

Evaluation

• Reading the ruler at eye level with a set square reduces parallax error.
• Exceeding the limit of proportionality permanently deforms the spring and invalidates later readings.
• Checking that the spring returns to its original length confirms the deformation was elastic.
• Repeats at each mass reduce random error in the length readings.

Common mistakes

• Plotting length instead of extension.
• Using mass in kilograms directly as the force in newtons.
• Ignoring the curve at high forces and forcing a straight line through all points.

Quick self-test

Linked topic: Forces and Motion revision

Aim

Test how acceleration depends on resultant force and on mass.

Method

1. Set up a trolley on a runway with a pulley at one end and light gates connected to a data logger.
2. Attach a string over the pulley to a hanging mass that provides the accelerating force.
3. Compensate for friction by tilting the runway slightly until the trolley moves at a steady speed when pushed.
4. Release the trolley and record the acceleration from the light gates.
5. To vary force, move masses from the trolley to the hanger so the total mass stays constant.
6. To vary mass, keep the hanging mass the same and add masses to the trolley.

Variables

Equipment

Trolley and runway, Pulley and string, Slotted masses and hanger, Light gates and data logger, Balance, Metre rule.

Results and observations

Acceleration is directly proportional to the resultant force when mass is constant, and inversely proportional to mass when force is constant.

Calculations

• F = m × a, so a = F ÷ m
• Weight of the hanging mass gives the accelerating force: W = m × g
• Acceleration from light gates: a = (v − u) ÷ t

Graphs and data

Plot acceleration against force for a straight line through the origin; plot acceleration against 1/mass for a straight line when force is constant.

Evaluation

• Moving masses from trolley to hanger keeps the total accelerating mass constant, which is the key control.
• Friction and air resistance reduce the measured acceleration, so the runway is tilted to compensate.
• Light gates measure more precisely and consistently than a stopwatch, removing reaction-time error.
• Repeats allow a mean acceleration at each setting.

Common mistakes

• Forgetting that the hanging mass is part of the mass being accelerated.
• Plotting acceleration against mass and expecting a straight line.
• Not compensating for friction, which shifts the line away from the origin.

Quick self-test

Linked topic: Forces and Motion revision

Aim

Measure wave speed for water waves and for waves on a stretched string.

Method

1. Ripple tank: set up the tank with a vibrating dipper and a lamp above so waves cast shadows on paper below.
2. Measure the length of, say, ten wave shadows and divide by ten to find the wavelength.
3. Find the frequency from the dipper setting, or by counting waves passing a point over a timed interval.
4. Stretched string: attach a string to a vibration generator with a mass hanging over a pulley to keep it taut.
5. Adjust the frequency until a clear standing wave pattern forms and measure the length of a whole number of half-wavelengths.
6. Calculate the wavelength and use the generator frequency to find the wave speed.

Variables

Equipment

Ripple tank with dipper and motor, Lamp and white paper, Signal generator and vibration generator, String, pulley and masses, Metre rule, Stopwatch.

Results and observations

Higher frequency gives a shorter wavelength for the same wave speed. Water waves slow down in shallower water.

Calculations

• v = f × λ
• Wavelength on a string = 2 × length of one loop (half-wavelength)
• Frequency by counting: f = number of waves ÷ time

Graphs and data

Plot wavelength against 1/frequency; a straight line through the origin has a gradient equal to the wave speed.

Evaluation

• Measuring across ten wavelengths and dividing reduces the percentage uncertainty in the wavelength.
• Ripple tank waves are hard to see clearly; a strobe or the shadow method makes them easier to measure.
• Water depth must be constant because it changes wave speed.
• The standing wave pattern must be stable before measuring, otherwise the wavelength reading is unreliable.

Common mistakes

• Measuring one loop of a standing wave and calling it the wavelength.
• Mixing units, for example wavelength in centimetres with speed in m/s.
• Counting waves for one second only, which gives a large percentage uncertainty.

Quick self-test

Aim

Compare how different surfaces reflect light and measure how light refracts when entering different materials.

Method

1. Place the object (mirror, or a glass or perspex block) on plain paper and draw around it.
2. Direct a ray of light from a ray box at the surface and mark the incident and emerging rays with crosses.
3. Remove the object and join the crosses with a ruler to draw the ray paths.
4. Draw the normal at 90 degrees to the surface at the point where the ray hits.
5. Measure the angles of incidence, reflection and refraction from the normal with a protractor.
6. Repeat for different angles of incidence and different materials or surfaces.

Variables

Equipment

Ray box with single slit, Glass and perspex blocks, Plane mirror and rough surfaces, Protractor and ruler, Plain paper and sharp pencil.

Results and observations

For reflection, the angle of reflection equals the angle of incidence. A smooth surface gives specular reflection; a rough surface scatters light (diffuse reflection). Light entering a denser material bends towards the normal and bends away on leaving.

Calculations

• No calculation is required at GCSE beyond comparing measured angles
• Compare the angle of refraction between materials at the same angle of incidence

Graphs and data

Plot angle of refraction against angle of incidence for each material and compare the curves.

Evaluation

• A sharp pencil and thin ray line reduce the uncertainty in the marked ray positions.
• The normal must be drawn at exactly 90 degrees or every angle is systematically wrong.
• Measuring angles from the surface instead of the normal is a systematic error.
• Repeating at several angles of incidence shows whether the pattern is consistent.

Common mistakes

• Measuring angles from the surface rather than the normal.
• Moving the block after drawing round it.
• Saying a rough surface does not reflect light, rather than that it scatters it.

Quick self-test

Aim

Compare how different surfaces emit or absorb infrared radiation.

Method

1. Fill a Leslie cube with hot water; its faces are matt black, shiny black, matt white and shiny metal.
2. Hold an infrared detector or thermometer a fixed distance from one face and record the reading after a set time.
3. Repeat for each face at the same distance and time.
4. For absorption, place identical sheets or flasks with different surfaces the same distance from a radiant heater.
5. Record the starting temperature and the temperature after a set time.
6. Compare the temperature rises for the different surfaces.

Variables

Equipment

Leslie cube, Infrared detector or thermometer, Ruler, Kettle, Radiant heater, Stopwatch, Test surfaces.

Results and observations

Matt black surfaces emit and absorb infrared radiation best; shiny, light-coloured surfaces are the poorest emitters and absorbers and the best reflectors.

Calculations

• Temperature rise = final temperature − starting temperature
• Mean readings from repeats for each surface

Graphs and data

Bar chart of detector reading or temperature rise for each surface makes the comparison clear.

Evaluation

• Distance must be identical for every face, because intensity falls rapidly with distance.
• The water cools during the experiment, so work quickly or refill between faces.
• The detector picks up background infrared from the room, so keep conditions constant.
• Repeats and a mean reduce random error in the detector readings.

Common mistakes

• Changing the distance between measurements.
• Assuming colour alone matters and ignoring whether the surface is matt or shiny.
• Comparing readings taken after different times.

Quick self-test

Linked topic: Energy revision