Experimental Design
Data Analysis
Measurement Techniques
Graphing Skills
Safety Protocols
100

What is a control variable?

A variable that is kept constant to ensure a fair test.

100

the graph of lg y against lg x is a straight line with slope 2. 

What does this tell us about the relationship between y and x?

y ∝ x2

100

A student investigates the relationship between the current through a resistor and the potential difference across it. What variables should be controlled during data collection?

Temperature of the resistor should be kept constant (e.g. by limiting current or switching off between readings), so resistance does not change.

100

A graph of log y vs log x is plotted, the line of best fit has gradient n and intercept c. Write the general relationship between y and x.

y=kxn 

100

What is the purpose of wearing goggles in a lab?

To protect eyes from harmful substances and splashes.

200

Describe the importance of repetition in experiments.

Repetition helps to verify results and improve reliability.

200

A student measures the current I in a circuit and plots a graph of current I against potential difference V. Each value of I has an uncertainty of ±0.02 A.

On the graph, how should the student represent this uncertainty?

By drawing vertical error bars of length ±0.02 A on each data point in the I-axis direction.

200

A student measures the diameter of a thin wire. Which instrument should be used, and why?

A micrometer screw gauge, because it has a resolution of 0.01 mm, suitable for very small diameters.

200

A graph of y against x is drawn with error bars. The line of best fit passes outside one of the error bars. What does this suggest about the data point?

That particular point is inconsistent within its stated uncertainty and may be anomalous.

200

A student heats water in a beaker with a Bunsen burner to measure how temperature affects solubility.

Use heat-resistant gloves/goggles, handle hot glassware carefully, and keep flammable materials away from the flame.

300

Define independent variable and provide an example.

The independent variable is the factor that is deliberately changed in an experiment to observe its effect on the dependent variable.

300

What is the “worst acceptable line?  

A straight line that still passes through all the error bars, but is drawn with the maximum or minimum possible gradient (steepest and shallowest line that still fits the data within the error bars).

300

A student measures the time for a trolley to travel down a slope. Why might light gates and a data logger be preferred over a handheld stopwatch?

Light gates reduce human reaction time error, providing more precise and reliable measurements.

300

Explain how to choose the scale for a graph.

Based on the range of data to ensure all points fit well


300

In a resistance experiment, a current is passed through a long wire. The student notices the wire becomes hot. 

What is the main hazard, and what precaution should be taken?

Hazard = burns/fire risk from hot wire. Precaution = use low currents, switch off between readings, and avoid touching the wire directly.

400

In an experiment investigating the effect of mass on the acceleration of an object, identify the independent and dependent variables.

The independent variable is the mass of the object, while the dependent variable is the acceleration of the object, measured in meters per second squared (m/s²).

400

How is worst acceptable line used to determine the uncertainty in the gradient?

  • Calculating the gradient of the line of best fit

  • Calculating the gradient of the worst acceptable line

  • The uncertainty in the gradient is then given by:

         Δm=∣m−mw∣

400

A student measures the resistance of a wire by plotting V against I. How should they reduce heating effects that could change resistance during data collection?

Switch off the power supply between readings, use low currents, and allow the wire to cool before repeating.

400

What is the purpose of a trend line?

To show the general direction of data points in a graph.


400

A student drops a steel ball bearing in oil to measure terminal velocity.

  • What hazard exists, and how can it be reduced?

Hazard = heavy/metal ball could shatter the container or spill oil. Precaution = use a deep, stable container, handle carefully, and mop spills immediately (oil is slippery).

500

In an experiment measuring the effect of different weights on the stretch of a rubber band, what could be a controlled variable, and why is it important to keep it constant?

One controlled variable could be the initial length of the rubber band before any weights are applied. It is important to keep this constant to ensure that any observed changes in stretch are solely due to the different weights applied, rather than variations in the starting length of the rubber band.



500

The pressure p of a fixed mass of gas is measured at different values of 1/V, where V is the volume.

  • What should be plotted to test Boyle’s law?

Plot p (y-axis) against 1/V (x-axis).

500

In a resonance experiment using a mass-spring system, the student varies the driving frequency and measures the amplitude of oscillation. How should they ensure reliable results around the resonance frequency?

Take closely spaced frequency readings near resonance, allow oscillations to settle before measuring amplitude, and repeat readings to reduce random error.

500

What is the importance of error bars?

They indicate the variability of data and the uncertainty in measurements.

500

In a light experiment, a ray box and power supply are used to shine bright light through a glass block.

  • What safety precaution should be observed?

Do not look directly into the light source; switch off the lamp when not in use to avoid overheating.

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