Required practicals — AQA GCSE Physics
The 7 required practicals on this course, as named in the specification.
Required practical activity 2 (physics only): investigate the effectiveness of different materials as thermal insulators and the factors that may affect the thermal insulation properties of a material.
In this required practical you compare insulating materials. Pour a fixed volume of hot water into a beaker, wrap it in the material being tested, fit a lid with a thermometer through it, and record the temperature every minute for ten minutes, or time how long it takes to fall by a set amount. The independent variable is the type of material, or its thickness if that is what you change; the dependent variable is the temperature drop in a set time, or the time for a set drop. Control the starting temperature, the volume of water, the beaker and the room. The material that keeps the water hottest has the lowest thermal conductivity. Repeat and average, because a single run hides how much readings scatter.
Go to Energy transfers in a systemRequired practical activity 4: use circuit diagrams to construct appropriate circuits to investiga the I–V characteristics of a variety of circuit elements, including a filament lamp, a diode and a resistor at constant temperature.
In this required practical you plot characteristics for three components: a resistor at constant temperature, a filament lamp and a diode. Build the same test circuit each time, with the component, an ammeter and a variable resistor in series and a voltmeter across the component, then adjust the variable resistor to take about ten pairs of readings. Reverse the connections to the supply to get negative values, which is essential for the diode, where the reverse readings are all 0.0 A. Plot current against potential difference for each component. A diode needs a protective resistor in series so the forward current cannot damage it, and the resistor must be given time to cool so its temperature stays constant.
Go to ResistorsRequired practical activity 5: use appropriate apparatus to make and record the measurements needed to determine the densities of regular and irregular solid objects and liquids. Volume shoul be determined from the dimensions of regularly shaped objects, and by a displacement technique for irregularly shaped objects. Dimensions to be measured using appropriate apparatus such as a ruler, micrometer or Vernier callipers.
Both methods start the same way: measure the mass on a balance and calculate density from ρ = m ÷ V. For a regular solid, measure the sides with a ruler, or with a micrometer or Vernier callipers for small dimensions, and calculate the volume from those dimensions, so for a cube V = side³. For an irregular solid such as a small statue you cannot calculate the volume, so use displacement: fill a eureka can to the spout, lower the object in until it is fully submerged, and collect the displaced water in a measuring cylinder, because the volume of water displaced equals the volume of the object. For a liquid, find the mass of an empty measuring cylinder, add the liquid, reweigh, and subtract.
Go to Density of materialsRequired practical activity 6: investigate the relationship between force and extension for a spring.
Clamp a spring from a stand with the base weighted or clamped to the bench so it cannot topple. Measure the unstretched length with a millimetre rule held vertically alongside, reading the position of the bottom of the spring at eye level to avoid parallax error. Add weights one newton at a time, measuring the new length after each and subtracting the original unstretched length to calculate the extension. Take readings as the weights are removed to check they match, ensuring no inelastic deformation. Plot force on the vertical axis against extension on the horizontal; the gradient of the straight part is the spring constant. The control variable is the spring itself. The graph curving at the top shows the limit of proportionality.
Go to Forces and elasticityRequired practical activity 7: investigate the effect of varying the force on the acceleration of an object of constant mass, and the effect of varying the mass of an object on the acceleration produced by a constant force.
This practical investigates Newton's Second Law, F = ma. You will use a trolley on a friction-compensated ramp, connected by a string over a pulley to suspended masses. To investigate varying force with constant mass, transfer masses one by one from the trolley to the weight hanger. This increases the accelerating force while keeping the total system mass constant. To investigate varying mass with constant force, keep the hanging mass constant and add masses directly to the trolley. Acceleration is measured using light gates and a data logger, or by timing the motion over a set distance. Plotting graphs of acceleration against force, and acceleration against inverse mass, should yield straight lines through the origin, confirming the relationships.
Go to Newton's Second LawRequired practical activity 8: make observations to identify the suitability of apparatus to measure the frequency, wavelength and speed of waves in a ripple tank and waves in a solid and take appropriate measurements.
Required practical 8 measures waves in two places. In a ripple tank, a motorised dipper makes straight ripples whose shadows fall on paper below; freeze them with a stroboscope or a photograph, measure across ten wavelengths with a rule and divide by ten, read the frequency from the motor's signal generator or count ripples passing a mark over 10 s, then use wave speed = frequency × wavelength. For waves in a solid, a vibration generator drives a stretched string until a clear standing pattern forms; the distance between adjacent nodes is half a wavelength, so λ = 2 × that spacing, and the frequency is read from the signal generator. Repeat each measurement and take a mean, and quote the resolution of the rule you used when you report the wavelength.
Go to Properties of wavesRequired practical activity 10: investigate how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface.
The standard version uses a Leslie cube: a metal cube with four faces, matt black, shiny black, matt white and shiny silver, filled with hot water. An infrared detector is placed a fixed distance from each face in turn and the reading recorded. The matt black face gives the highest reading and the shiny silver face the lowest, showing that a matt black surface is the best emitter of infrared and a shiny silver one the worst. The absorption version uses flasks or metal plates with different surfaces the same distance from a heater, measuring the temperature rise over a fixed time; the matt black one warms fastest. The control variables matter: the same water temperature, the same distance, the same starting temperature and the same time interval.
Go to Properties of electromagnetic waves 1
Practise the questions examiners set on these practicals.
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