AQA A-level Physics required practicals
12 practicals. Check the reasoning behind your results.
Check your practical reasoning
Question 1 of 5
A student times 20 complete pendulum oscillations as (32.0 ± 0.4) s. What is the period, with its absolute uncertainty?
| Measurement | Value |
|---|---|
| Oscillations | 20 |
| Total time | (32.0 ± 0.4) s |
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The 12 required practicals
Try the free stationary waves walkthrough1Vary the length, tension and mass per unit length of a stretched string and measure the frequency of its stationary waves
What to practise
Exam questions ask: Frequency against each controlled quantity; identify the mode and effective length; plot linearised graphs such as f against 1/l.
Where marks go: Using the total wire length, or the hanging mass, as if it were the mass per unit length of the string.
2Young's double-slit interference and a diffraction grating: measure fringe and angle geometry to find wavelength
What to practise
Exam questions ask: Slit or grating spacing, averaged fringe spacing over several fringes, order angles; wavelength from both methods with a check on the small-angle approximation.
Where marks go: Treating lines per millimetre as the grating spacing in metres; using the small-angle formula where the geometry does not allow it; ignoring laser safety.
3Determine g by a free-fall method
What to practise
Exam questions ask: Displacement against time squared; g from twice the gradient; release delay, position reference and repeatability.
Where marks go: Forgetting the factor of one half; calling a reaction delay random when it adds the same time to every reading.
4Determine the Young modulus of a wire by a simple method
What to practise
Exam questions ask: Stress against strain or extension against load; Young modulus from the gradient and the wire's geometry.
Where marks go: Treating the stiffness of one wire as the Young modulus of the material; using the diameter as the radius; loading beyond the limit of proportionality.
5Determine the resistivity of a wire using a micrometer, ammeter and voltmeter
What to practise
Exam questions ask: Resistance from V over I for each length; resistivity from the gradient of R against length times the cross-sectional area.
Where marks go: Ignoring that the diameter uncertainty is doubled in the area; treating resistance per metre as resistivity; letting the wire heat up.
6Investigate the emf and internal resistance of electric cells and batteries
What to practise
Exam questions ask: Plot V against I: the intercept is the emf and the gradient is minus the internal resistance.
Where marks go: Treating a loaded terminal voltage as the emf; drawing the voltmeter across the wrong components.
7Investigate the time period of a mass-spring system and of a simple pendulum
What to practise
Exam questions ask: Period squared against mass and against length; spring constant and g from the gradients.
Where marks go: Timing too few oscillations; using large amplitudes where the pendulum is no longer simple harmonic.
8Investigate Boyle's law (constant temperature) and Charles's law (constant pressure) for a gas
What to practise
Exam questions ask: p against 1/V for Boyle's law; V against temperature and its extrapolation to absolute zero for Charles's law.
Where marks go: Using Celsius in a proportional gas relation; confusing force with pressure; reading before the gas reaches thermal equilibrium.
9Investigate the charge and discharge of capacitors, using a log-linear graph to find the time constant
What to practise
Exam questions ask: ln V against t is a straight line of gradient minus 1/RC; time constant from the gradient or from the time to fall to 37%.
Where marks go: Treating the time constant as the half-life; confusing the capacitor's voltage with the resistor's voltage while charging.
10Investigate how the force on a wire varies with flux density, current and length using a top-pan balance
What to practise
Exam questions ask: Balance reading converted to force; force against current, with gradient B times the length of wire in the field.
Where marks go: Using the whole wire length instead of the length in the field; treating a reading in grams as a force in newtons.
11Investigate how the emf induced in a search coil varies with the angle between the coil and a magnetic field
What to practise
Exam questions ask: Peak emf against the cosine of the angle between the field and the normal to the coil.
Where marks go: Measuring the angle from the plane of the coil instead of its normal; treating a steady flux as a source of induced emf.
12Investigate the inverse-square law for gamma radiation
What to practise
Exam questions ask: Corrected count rate against distance; 1 over the square root of the corrected rate against distance is a straight line whose intercept gives the offset of the source inside its holder.
Where marks go: Forgetting to subtract background; rejecting a trend because two products differ within counting uncertainty; unsafe handling of the source.