Edexcel GCSE Physics Core Practicals: Complete Revision Guide

If you are studying Edexcel GCSE Physics (1PH0), core practicals are among the most predictable marks available across both exam papers. There are eight core practicals in total, and Edexcel requires that at least 15% of marks across the qualification assess practical skills. That means a minimum of 30 marks out of 200 are directly tied to your understanding of how physics investigations work, with core practicals forming the foundation of those questions.

There is no coursework or controlled assessment in Edexcel GCSE Physics. Your understanding of these practicals is tested entirely through written exam questions. You need to know far more than what you did in the lesson. You need to understand the aim, the full method, the variables, the expected results, how to process data, what could go wrong, and how to improve the investigation. This guide covers all eight core practicals in the detail the examiners expect.

For a broader overview of the full specification, see our Edexcel GCSE Physics revision guide.

How Core Practicals Are Examined

Core practical questions can appear on either Paper 1 or Paper 2, though they are most likely to appear on the paper covering the relevant topic area. Paper 1 examines Topics 1-5 (key concepts, motion and forces, conservation of energy, waves, and light and the electromagnetic spectrum), while Paper 2 examines Topics 6-8 (radioactivity, astronomy, and energy -- forces doing work). Paper 2 also includes synoptic questions that can draw on any content from the course.

The types of questions you will face include:

• Describe the method -- writing out the steps of a practical in a clear, logical order.
• Identify variables -- naming the independent, dependent, and control variables.
• Analyse data -- reading tables and graphs, calculating values, identifying trends and anomalies.
• Evaluate results -- discussing accuracy, reliability, sources of error, and suggesting specific improvements.
• Apply to unfamiliar contexts -- using your understanding of a core practical to interpret a new experimental scenario you have not seen before.

The last type is where higher-grade marks are found. Edexcel frequently presents a variation of a core practical and asks you to apply your understanding to it. If you truly understand the principles behind each practical, these questions are straightforward. If you have only memorised the steps, they are much harder.

For guidance on interpreting exam questions effectively, see our guide to Edexcel GCSE exam command words.

How to Answer "Describe the Method" Questions

These questions are typically worth 6 marks and follow a predictable structure. To score full marks:

1. State what you would change (independent variable) and how you would change it.
2. State what you would measure (dependent variable) and what equipment you would use.
3. List at least two variables you would keep the same (control variables) and explain how.
4. Include specific detail -- masses, distances, voltages, time intervals.
5. State that you would repeat the experiment at least three times and calculate a mean.
6. Describe how you would present the results (table, graph type).

Write your answer as a numbered method, not a paragraph. This makes it easier for the examiner to award marks and harder for you to miss steps.

The 8 Edexcel GCSE Physics Core Practicals

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CP1: Investigating the Relationship Between Force and Extension (Hooke's Law)

Aim: To investigate how the extension of a spring depends on the applied force and to determine the spring constant.

Equipment: Helical spring, clamp stand with clamp and boss, metre ruler, set of slotted masses and mass hanger, pointer (attached to the bottom of the spring to aid reading), safety goggles, cushion or sand tray beneath the spring.

Method:

1. Set up the clamp stand on the bench and clamp the spring securely at the top so it hangs vertically.
2. Attach a pointer to the bottom of the spring to make readings easier. Place the metre ruler vertically alongside the spring using a second clamp.
3. Record the position of the pointer with no load on the spring. This is the original length.
4. Add a mass hanger and record the new pointer position. Calculate the extension by subtracting the original length from the new length.
5. Continue adding equal masses one at a time (e.g. 1 N increments), recording the pointer position after each addition. Calculate the extension for each load.
6. Continue until at least 8 readings have been taken or the spring has clearly passed its limit of proportionality (the extension per unit force starts to increase).
7. Unload the masses in the same increments, recording the pointer position at each stage. Check whether the spring returns to its original length.
8. Repeat the entire experiment at least three times and calculate mean extensions.

Variables:

• Independent variable: Force applied to the spring (weight of the masses in newtons).
• Dependent variable: Extension of the spring (in metres or centimetres).
• Control variables: Same spring throughout, same ruler, same starting position, masses added and removed carefully without bouncing.

Expected results: Up to the limit of proportionality, force and extension are directly proportional: F = kx, where k is the spring constant. The force-extension graph is a straight line through the origin in this region. Beyond the limit of proportionality, the spring no longer obeys Hooke's law and the line curves, with greater extension for each additional unit of force. The spring may not return to its original length if the elastic limit has been exceeded.

Processing results: Plot a graph of force (y-axis) against extension (x-axis). The gradient of the straight-line section equals the spring constant, k, measured in N/m. Identify the limit of proportionality as the point where the line begins to curve.

Sources of error and improvements:

• Parallax error when reading the ruler -- position the eye level with the pointer and read perpendicular to the ruler scale.
• The spring may oscillate after adding masses -- wait for the spring to come to rest before taking the reading.
• The spring may have been permanently deformed if the elastic limit was exceeded -- use a new spring if repeat experiments show the spring does not return to its original length.
• Masses may not be accurate -- check using a balance before starting.

Exam question types: Plot a force-extension graph from given data. Identify the limit of proportionality on the graph. Calculate the spring constant from the gradient. Explain the difference between the limit of proportionality and the elastic limit. State what happens to the spring beyond the elastic limit (it is permanently deformed and does not return to its original length when the force is removed). Calculate the energy stored in a spring using E = 0.5 x k x x squared.

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CP2: Investigating the Effectiveness of Different Insulating Materials

Aim: To investigate how effective different materials are at reducing the rate of heat loss from a container of hot water.

Equipment: Beakers (or boiling tubes), thermometer or temperature probe, stopwatch, measuring cylinder, kettle (for hot water), elastic bands or tape, a selection of insulating materials (e.g. cotton wool, bubble wrap, newspaper, felt, aluminium foil), lid (to reduce convection losses).

Method:

1. Wrap one beaker in a layer of the first insulating material. Secure it with elastic bands or tape. Ensure the thickness of the wrapping is the same for each material.
2. Measure a fixed volume of hot water (e.g. 100 cm cubed) using a measuring cylinder and pour it into the wrapped beaker.
3. Place a lid on the beaker and insert the thermometer through a hole in the lid.
4. Record the starting temperature of the water.
5. Record the temperature every minute for a fixed time period (e.g. 10 minutes).
6. Repeat the experiment with each insulating material, and once with no insulation as a control.
7. Repeat each test at least three times and calculate mean temperature drops.

Variables:

• Independent variable: Type of insulating material (or, in an alternative version, thickness of the same material).
• Dependent variable: Temperature drop over the fixed time period (or temperature at set time intervals).
• Control variables: Volume of water, starting temperature of water, type and size of beaker, thickness of insulating material, whether a lid is used, room temperature.

Expected results: The beaker with no insulation loses heat most rapidly and shows the greatest temperature drop. Materials that trap air effectively (such as cotton wool or bubble wrap) are the best insulators, producing the smallest temperature drop. Aluminium foil reduces heat loss by radiation but is less effective at reducing conduction and convection.

Processing results: Plot a cooling curve for each material (temperature on the y-axis, time on the x-axis). Alternatively, present the total temperature drop for each material in a bar chart for direct comparison.

Sources of error and improvements:

• If the lid is not fitted properly, heat escapes by convection from the top -- use a tight-fitting lid with only a small hole for the thermometer.
• The thermometer may not be stirred, giving readings that reflect only the temperature of the water nearest the thermometer rather than the bulk temperature -- stir gently before each reading or use a temperature probe with a data logger.
• Different starting temperatures between trials affect the rate of cooling (a hotter object loses heat faster) -- ensure all trials start at the same temperature.
• Room temperature may vary between trials -- carry out all tests in the same session and record room temperature.

Exam question types: Explain why trapped air makes a good insulator (air is a poor conductor and the trapped pockets prevent convection currents). Compare the effectiveness of different materials from provided data. Explain how to ensure a fair test. Describe how heat is lost from the beaker by conduction, convection, and radiation. Suggest why aluminium foil works differently from fibrous materials.

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CP3: Investigating the Relationship Between Force, Mass and Acceleration (Newton's Second Law)

Aim: To investigate the relationship between the net force acting on an object, its mass, and its acceleration, and to verify F = ma.

Equipment: Dynamics trolley, runway (smooth track), pulley and string, slotted masses (for the hanging mass and for adding to the trolley), light gates and data logger (or ticker tape and ticker timer), ruler, balance, card of known length (to interrupt the light gates).

Method:

1. Set up a smooth runway on the bench. Attach a pulley to one end.
2. Place the trolley on the track. Attach a string from the trolley, over the pulley, to a hanging mass.
3. Fix a piece of card of known length to the top of the trolley so it passes through the light gates. Position two light gates along the track.
4. Compensate for friction by raising the end of the track without the pulley very slightly until the trolley, when given a small push, moves at a constant speed along the track (the component of gravity along the slope balances friction).
5. To investigate the effect of force on acceleration (constant total mass): transfer masses from the trolley to the hanging mass one at a time, keeping the total mass of the system (trolley plus hanging mass) constant. Record the acceleration for each hanging mass.
6. To investigate the effect of mass on acceleration (constant force): keep the hanging mass the same but add masses to the trolley to increase the total mass. Record the acceleration for each total mass.
7. Release the trolley from the same starting position each time. The data logger calculates acceleration from the light gate timings and the card length.
8. Repeat each measurement at least three times and calculate a mean acceleration.

Variables:

• Independent variable: Force (weight of the hanging mass) when investigating force, or total mass of the system when investigating mass.
• Dependent variable: Acceleration of the trolley.
• Control variables: Total system mass (when varying force), applied force (when varying mass), starting position, friction compensation.

Expected results: At constant mass, acceleration is directly proportional to the net force (a straight line through the origin on an acceleration-force graph). At constant force, acceleration is inversely proportional to mass (a curve on an acceleration-mass graph that becomes a straight line through the origin when acceleration is plotted against 1/mass).

Processing results: For the force investigation, plot acceleration (y-axis) against force (x-axis). The gradient equals 1/mass. For the mass investigation, plot acceleration against 1/mass. The gradient equals the net force.

Sources of error and improvements:

• Friction acts on the trolley, reducing the net force -- compensate by tilting the track slightly so the gravitational component along the slope opposes friction.
• The string may not be horizontal from the trolley to the pulley -- keep the string as close to parallel with the track as possible to ensure the full weight of the hanging mass acts as the accelerating force.
• The card may not cleanly interrupt the light gates -- ensure the card is flat and wide enough to trigger both light gates reliably.
• The mass of the string is usually ignored, but for very light hanging masses it could become significant -- use a light, inextensible string.

Exam question types: Calculate acceleration from force and mass using F = ma. Explain why the total mass must remain constant when investigating the effect of force. Explain why the track is tilted to compensate for friction. Describe how light gates measure acceleration. Plot and interpret graphs of acceleration against force or acceleration against 1/mass. Explain why the measured acceleration may be less than the predicted value (due to friction not being fully compensated).

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CP4: Investigating Specific Heat Capacity

Aim: To determine the specific heat capacity of a metal block (or water) by measuring the temperature change produced by a known amount of electrical energy.

Equipment: Metal block (e.g. aluminium or copper) with two holes drilled in it (one for a heater and one for a thermometer), electric immersion heater, thermometer or temperature probe, power supply, ammeter, voltmeter, connecting wires, stopwatch, joulemeter (if available), balance, insulating material (e.g. lagging).

Method:

1. Measure the mass of the metal block using a balance. Record this value in kilograms.
2. Insert the electric immersion heater into one hole and the thermometer into the other. Add a small amount of oil or water to the thermometer hole to improve thermal contact.
3. Wrap the block in insulating material to reduce heat loss to the surroundings.
4. Record the starting temperature of the block.
5. Connect the heater to the power supply in series with an ammeter. Connect a voltmeter in parallel across the heater.
6. Switch on the power supply and start the stopwatch simultaneously.
7. Record the ammeter reading (current, I) and the voltmeter reading (voltage, V) at regular intervals. If they remain constant, a single reading is sufficient.
8. After a set time (e.g. 10 minutes), switch off the power supply and record the highest temperature reached.
9. Calculate the energy supplied using E = V x I x t (or read from a joulemeter).
10. Calculate the specific heat capacity using the equation: c = E / (m x delta theta), where delta theta is the temperature change.

Variables:

• Independent variable: This is typically a measurement practical rather than an investigation -- but if comparing materials, the independent variable is the type of metal.
• Dependent variable: Temperature change of the block for a given energy input.
• Control variables: Energy supplied, mass of block (or if comparing materials, use blocks of the same mass), insulation, starting temperature.

Expected results: The temperature of the block rises as energy is supplied. Aluminium has a specific heat capacity of approximately 900 J/kg/degrees Celsius, and copper approximately 390 J/kg/degrees Celsius. The calculated value is likely to be higher than the accepted value because some energy is lost to the surroundings rather than heating the block.

Processing results: Calculate the specific heat capacity using c = E / (m x delta theta). Compare the experimental value with the accepted value and calculate the percentage error.

Sources of error and improvements:

• Heat is lost to the surroundings, meaning not all the electrical energy heats the block -- wrap the block in insulation to reduce heat loss.
• Some energy heats the heater element itself rather than the block -- this cannot be fully eliminated, but using a block with a snug-fitting heater hole and good thermal contact reduces the effect.
• Thermometer lag means the block may continue to heat after the heater is switched off -- wait for the temperature to stabilise and record the maximum temperature reached after switching off.
• Poor thermal contact between the heater or thermometer and the block -- add a few drops of oil to fill the gap in the drilled holes.

Exam question types: Calculate specific heat capacity from given values of energy, mass, and temperature change using c = E / (m x delta theta). Rearrange the equation to find any of the four quantities. Explain why the experimental value differs from the accepted value. Describe specific improvements to reduce energy losses. Explain why insulation is important. Calculate the energy supplied using E = VIt.

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CP5: Investigating I-V Characteristics of Circuit Components

Aim: To investigate how the current through a component varies with the potential difference across it for a resistor, a filament lamp, and a diode.

Equipment: Battery or DC power supply, variable resistor (or variable power supply), ammeter, voltmeter, connecting wires, component holder, test components (resistor, filament lamp, diode), switch.

Method:

1. Set up a series circuit with the power supply, a switch, the variable resistor, the ammeter, and the component being tested all in series.
2. Connect the voltmeter in parallel across the component being tested.
3. Close the switch and adjust the variable resistor to its maximum resistance. Record the ammeter reading (current) and the voltmeter reading (potential difference).
4. Gradually decrease the resistance of the variable resistor to increase the potential difference across the component. At each setting, record the current and the potential difference.
5. Take at least six pairs of readings across the full range of the variable resistor.
6. Reverse the connections to the power supply (swap the positive and negative terminals) and repeat, recording negative values of both current and potential difference. This is essential for the diode.
7. Repeat the full set of readings at least three times and calculate mean values.
8. Repeat the entire procedure for each component.

Variables:

• Independent variable: Potential difference across the component (varied using the variable resistor).
• Dependent variable: Current through the component.
• Control variables: Same component throughout each test, room temperature (particularly important for the resistor), same circuit components.

Expected results:

• Resistor (ohmic conductor): The I-V graph is a straight line through the origin. Current is directly proportional to potential difference. The resistance is constant and equals the reciprocal of the gradient. The graph is symmetrical when the voltage is reversed.
• Filament lamp: The I-V graph is a curve that passes through the origin. At low voltages, the graph is approximately linear, but as the voltage increases, the current increases less steeply. This is because the filament heats up, increasing its resistance. The graph is symmetrical when the voltage is reversed.
• Diode: The I-V graph shows that the diode conducts in one direction only (forward bias). In the forward direction, very little current flows until the threshold voltage (approximately 0.7 V for a silicon diode) is reached, after which the current increases rapidly. In reverse bias, no current flows (or a negligibly small current).

Processing results: Plot I-V graphs for each component with potential difference (V) on the x-axis and current (I) on the y-axis. Calculate resistance at any point using R = V/I.

Sources of error and improvements:

• The filament lamp heats up during the experiment, which changes its resistance -- take readings quickly or allow the lamp to cool between readings.
• Connections may be loose, introducing extra resistance -- ensure all connections are tight and use clean contacts.
• The ammeter and voltmeter have internal resistance that can affect readings -- for most GCSE-level experiments, this effect is small, but using an ammeter with very low resistance and a voltmeter with very high resistance minimises the error.
• Taking too few readings makes it difficult to identify the shape of the curve -- take at least six readings across the full range in each direction.

Exam question types: Sketch the I-V characteristic for a resistor, filament lamp, or diode. Explain why the resistance of a filament lamp increases as the current increases (the filament gets hotter, metal atoms vibrate more, and free electrons collide with them more frequently). Explain why a diode only conducts in one direction. Calculate resistance from an I-V graph using R = V/I. Describe the circuit needed to obtain the I-V characteristic, including the positions of the ammeter and voltmeter.

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CP6: Investigating How the Resistance of a Wire Depends on Its Length

Aim: To investigate the relationship between the length of a wire and its resistance, and to confirm that resistance is directly proportional to length for a wire of uniform cross-sectional area.

Equipment: Constantan wire (or nichrome wire), metre ruler, crocodile clips, ammeter, voltmeter, power supply, connecting wires, switch, micrometer or vernier calipers (to measure wire diameter).

Method:

1. Tape or fix the constantan wire along the length of a metre ruler.
2. Connect the power supply, switch, and ammeter in series with the wire. Connect the voltmeter in parallel across the section of wire being tested.
3. Use crocodile clips to connect the circuit to the wire at the desired length (e.g. 10 cm).
4. Close the switch and record the ammeter reading (current) and the voltmeter reading (potential difference). Switch off promptly to prevent the wire from heating up.
5. Calculate the resistance using R = V / I.
6. Move one crocodile clip to increase the length of wire in the circuit (e.g. 20 cm, 30 cm, 40 cm, up to 100 cm). At each length, record V and I and calculate R.
7. Repeat the experiment at least three times at each length and calculate mean resistance values.
8. Measure the diameter of the wire at several points using a micrometer, and calculate the mean diameter to confirm the wire has a uniform cross-section.

Variables:

• Independent variable: Length of the wire (in cm or m).
• Dependent variable: Resistance of the wire (in ohms).
• Control variables: Material of the wire, cross-sectional area (diameter) of the wire, temperature of the wire (switch off between readings to prevent heating).

Expected results: Resistance is directly proportional to the length of the wire. A graph of resistance (y-axis) against length (x-axis) is a straight line through the origin. Doubling the length doubles the resistance. This is because a longer wire has more ions for the electrons to collide with as they travel through, increasing the opposition to current flow.

Processing results: Plot resistance against length. The graph should be a straight line through the origin. Calculate the gradient, which equals the resistance per unit length (in ohms per metre). Using R = rho x L / A, the resistivity (rho) of the wire can be calculated if the cross-sectional area is known.

Sources of error and improvements:

• The wire heats up when current flows through it, which changes its resistance -- keep the current low and switch off between readings to allow the wire to cool.
• Poor contact between the crocodile clips and the wire adds extra resistance at the connections -- ensure clips are firmly attached and use clean wire at the contact points.
• Parallax error when measuring the length of wire between the clips -- measure from the inside edge of one clip to the inside edge of the other, at eye level.
• The wire may not be perfectly straight, giving a length that differs from the actual length of wire in the circuit -- tape the wire along the ruler under slight tension to keep it straight.

Exam question types: Plot a graph of resistance against length from given data. Calculate resistance using R = V/I. Explain why resistance increases with length (more collisions between free electrons and metal ions over a greater distance). Explain why the wire should be kept at a constant temperature. Describe how to improve the experiment for greater accuracy. Use the equation R = rho x L / A to calculate resistivity.

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CP7: Investigating the Absorption and Emission of Infrared Radiation

Aim: To investigate how the nature of a surface affects the absorption and emission of infrared radiation.

Equipment: Leslie cube (a hollow metal cube with four different surfaces: matt black, shiny silver or metallic, matt white, and shiny black), kettle (for hot water), infrared detector (or thermometer with a blackened bulb), ruler, stopwatch.

Method (emission):

1. Fill the Leslie cube with hot water from a kettle and place the lid on top.
2. Allow the cube to stand for two minutes so that all four faces reach the same temperature.
3. Position the infrared detector at a fixed, equal distance (e.g. 5 cm) from one face of the cube. Record the infrared reading.
4. Without moving the cube, rotate the detector (or move it) to the same distance from each of the other three faces in turn. Record the infrared reading for each face.
5. Repeat the readings at least three times for each face and calculate a mean.

Method (absorption -- alternative investigation):

1. Place identical containers of water behind plates of different surface colours and finishes.
2. Position a radiant heat source at equal distance from each plate.
3. Measure the temperature rise of the water behind each plate over a fixed time period.

Variables:

• Independent variable: Type of surface (matt black, shiny silver, matt white, shiny black).
• Dependent variable: Infrared radiation detected (emission) or temperature rise of water (absorption).
• Control variables: Distance of detector from the face, temperature of water in the Leslie cube, time allowed for the cube to reach thermal equilibrium, same infrared detector used throughout.

Expected results: Matt black surfaces are the best emitters and the best absorbers of infrared radiation. Shiny silver or metallic surfaces are the worst emitters and the worst absorbers (they are the best reflectors). Matt white and shiny black surfaces fall between these two extremes. The key factor is the colour and texture: dark, matt surfaces emit and absorb more infrared radiation than light, shiny surfaces.

Processing results: Present the infrared detector readings in a table and as a bar chart comparing the four surfaces. Rank the surfaces from best to worst emitter.

Sources of error and improvements:

• The detector may not be at exactly the same distance from each face -- use a ruler to measure the distance carefully each time and clamp the detector in position.
• The water temperature may drop during the experiment, meaning later readings are taken at a lower temperature than earlier ones -- take readings quickly or re-check the temperature and repeat if it has dropped significantly.
• Background infrared radiation from radiators, windows, or other heat sources may affect the readings -- carry out the experiment away from other heat sources, or take a background reading and subtract it.
• Air currents may carry heat away unevenly -- perform the experiment in a draught-free environment.

Exam question types: State which surface is the best and worst emitter of infrared radiation. Explain why matt black surfaces are good emitters and absorbers. Describe a practical application of this knowledge (e.g. solar panels are matt black to absorb maximum radiation; radiators are often painted white for aesthetics, but would be more efficient if matt black). Explain how the experiment could be improved for reliability. Describe how to test absorption as well as emission.

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CP8: Investigating the Relationship Between Light Intensity and Distance (Inverse Square Law)

Aim: To investigate how light intensity varies with distance from a light source and to test the inverse square law relationship.

Equipment: Light source (ray box or lamp with a single clear filament), LDR (light-dependent resistor) connected to an ohmmeter or multimeter, or a light meter/lux meter, metre ruler, darkened room or light-proof box, clamp and stand.

Method:

1. Set up the light source at one end of a ruler in a darkened room. Position the LDR (or light meter) at a measured distance from the light source.
2. Record the distance from the light source to the LDR and the corresponding light intensity reading (or resistance of the LDR -- note that lower resistance corresponds to higher light intensity).
3. Move the LDR to a new distance (e.g. increase by 5 cm or 10 cm at a time) and record the new distance and light intensity.
4. Continue until you have at least 8 readings covering a wide range of distances (e.g. 10 cm to 100 cm).
5. Repeat each reading at least three times and calculate a mean.

Variables:

• Independent variable: Distance from the light source to the LDR (in cm or m).
• Dependent variable: Light intensity (measured by a light meter in lux, or inferred from the resistance of the LDR).
• Control variables: Same light source at the same brightness (constant voltage), same LDR or light meter, background light level (use a darkened room), alignment of the LDR so it faces the light source directly.

Expected results: Light intensity decreases as distance from the source increases. Specifically, intensity is inversely proportional to the square of the distance: I is proportional to 1/d squared. This means that doubling the distance reduces the intensity to one quarter. A graph of intensity against distance shows a curve. A graph of intensity against 1/d squared is a straight line through the origin, confirming the inverse square law.

Processing results: Plot light intensity against distance to show the non-linear relationship. Then plot light intensity against 1/d squared. If the inverse square law holds, this second graph is a straight line through the origin. If using an LDR, plot 1/resistance against 1/d squared (since lower resistance means higher intensity).

Sources of error and improvements:

• Background light from windows, screens, or other sources interferes with readings -- conduct the experiment in a fully darkened room or use a light-proof tube around the LDR.
• The LDR may not be aligned perpendicular to the light source -- use a clamp to hold the LDR in a fixed orientation, facing directly towards the lamp.
• At very short distances, the light source cannot be treated as a point source, and the inverse square law breaks down -- avoid taking readings very close to the source.
• The light source may warm up and change brightness over time -- allow the lamp to warm up for several minutes before starting and check that the voltage remains constant.
• Measuring distance from the wrong point (e.g. the edge of the lamp rather than the filament) introduces a systematic error -- measure from the filament of the lamp to the surface of the LDR.

Exam question types: State the inverse square law relationship. Explain what happens to light intensity when the distance is tripled (it falls to 1/9 of the original value). Plot and interpret a graph of intensity against 1/d squared. Calculate light intensity at a given distance using the inverse square law. Describe how to set up this experiment and ensure valid results. Explain why a darkened room is necessary. Link this practical to real-world contexts such as the apparent brightness of stars at different distances.

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General Practical Skills Across All Core Practicals

Beyond the specific core practicals, Edexcel tests a range of general practical skills. Understanding these terms is essential for picking up marks on any practical question.

Accuracy means how close a measurement is to the true value. Use calibrated, appropriate equipment and correct technique to improve accuracy.

Precision means how close repeated measurements are to each other. A set of results can be precise (tightly clustered) but inaccurate (far from the true value) if there is a systematic error.

Reliability means that results are consistent when the experiment is repeated. Carry out at least three repeats and calculate a mean, discarding anomalous results.

Resolution is the smallest change a measuring instrument can detect. A micrometer that reads to 0.01 mm has higher resolution than a ruler that reads to 1 mm. Using higher resolution equipment increases precision.

Anomalous results are values that do not fit the overall pattern. Identify them, suggest a possible cause, and exclude them from your mean calculation.

Valid conclusion -- a conclusion is valid if it is supported by the data and the experiment was a fair test where only the independent variable was changed.

Reproducibility means that other scientists can obtain the same results using the same method. This is improved by writing clear, detailed methods and using standardised equipment and techniques.

Zero error -- a systematic error caused by an instrument not reading zero when it should. For example, a balance that reads 0.2 g with nothing on it, or a ruler where the zero mark is worn away. Always check for zero errors before starting and subtract them from your readings.

How to Answer Practical Questions in the Exam

Practical questions in Edexcel GCSE Physics follow predictable patterns. Here is how to approach each type.

"Describe the method" questions (typically 6 marks): Write the steps in a logical order, as if giving instructions to someone who has never done the practical. Include specific details: distances, masses, voltages, time intervals, equipment names. State how you would ensure a fair test (control variables) and improve reliability (repeats and means). Do not just list equipment -- describe what you do with it.

"Identify the variables" questions (typically 1-3 marks): State the independent, dependent, and control variables clearly. Use the exact wording from the question where possible. For example, if the question says "the student changed the length of the wire," your independent variable is the length of the wire.

"Analyse the data" questions (typically 2-4 marks): Describe the trend or pattern shown in the data. Use specific figures from the table or graph to support your answer. If asked to calculate a mean, show your working. If asked to identify an anomaly, state which value it is and suggest a possible cause.

"Evaluate the method" questions (typically 3-6 marks): Comment on sources of error and suggest specific improvements. Avoid vague statements like "human error." Be specific: "The wire heats up as current flows through it, increasing its resistance and giving a higher reading than expected; to reduce this, keep the current low and switch off between readings to allow the wire to cool." Always link your evaluation to the specific practical being discussed.

"Explain the results" questions (typically 2-4 marks): Connect the practical observations to the underlying physics. For Hooke's law, link to the proportional relationship between force and extension. For Newton's second law, link F = ma. For I-V characteristics, explain resistance changes in terms of particle collisions and temperature. The mark scheme rewards physical explanation, not just description of what happened.

For further guidance on command words and what examiners expect, see our command words guide. For a detailed look at how mark schemes allocate marks, see our guide on how Edexcel mark schemes work.

Final Advice

Core practicals are not something to revise the night before the exam. They require genuine understanding of both the practical method and the underlying physics. Start by writing out each practical from memory: the aim, equipment, method, variables, expected results, and at least two improvements. Then check against this guide and fill in the gaps.

Next, practise applying your knowledge to unfamiliar scenarios. Edexcel past papers frequently present variations of core practicals -- a different material in the insulation investigation, a different component for I-V characteristics, an unfamiliar context for the inverse square law -- and ask you to apply the same principles. This is where the higher-grade marks are found, and it is where students who truly understand the practicals pull away from those who have only memorised the steps.

Use past papers and mark schemes from Edexcel to see exactly how questions are worded and what the examiners expect. Pay particular attention to the 6-mark extended response questions, which require clear, logical writing with correct scientific terminology.

For targeted exam practice across the full Edexcel GCSE Physics specification, explore LearningBro's Edexcel GCSE Physics courses and our Physics revision guide. For all available Edexcel courses and revision resources, visit our Edexcel page.