AQA GCSE Physics Practicals

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Define the “Specific Heat Capacity” of a substance

The amount of energy needed to raise the temperature of 1 kilogram of a
substance by 1 degree Celsius.

State the units for Specific Heat Capacity

J/°C/kg
Joules/Degree Celsius/Kilogram

State the equation used to calculate the temperature change when a substance is heated.

ΔE = m c Δ𝛉
Energy change = mass x SHC x temperature change

If the power of the heater being used isn’t given, how can you calculate it?

By connecting it in parallel with a voltmeter, and in series with an ammeter, and then applying the equation P = IV

Why do the metal blocks used in the experiment have two holes in them?

One for is for the heater and one is for the thermometer

What can be done to improve the reading given by the thermometer?

Add a few drops of water in the hole with the thermometer to improve the thermal contact and ensure even heating.

What reading do you record during the experiment and how frequently?

You record the temperature value every 10 minutes from when the heater is inserted and switched on.

What graph do you plot with the data?

A graph of temperature against work done by the heater.

How do you calculate the work done by the heater?

Using the equation:
Energy = Power of heater x Time
Where energy is equivalent to the work done.

Once the block has initially warmed up, describe the graph of temperature against work done by the heater that should be obtained.

It should be a linear relationship and so should produce a straight line.

If you start timing from when you switch on the heater, why may the graph not initially be linear?

There will initially be some thermal inertia whilst the block and heater warm up.

What does the gradient of the graph represent?

The inverse of the heat capacity for the metal block.

How do you obtain the specific heat capacity for the metal you are measuring?

Divide the inverse of the gradient by the mass of the metal block used.

What is the difference between heat capacity and specific heat capacity?

Specific heat capacity is the heat capacity measured for a mass of 1 kg

Why should you wrap insulation around the outside of the metal block?

To reduce the heat loss to the environment and ensure the temperature reading is as accurate as possible.

What safety precautions should be taken when carrying out this experiment?

● Avoid touching the metal
● Use a heatproof mat
● Avoid spilling water near the power supply
when adding drops to the thermometer hole

Outline the basic steps of the thermal insulation practical.

1. Wrap glass beakers with different insulating materials
2. Boil water in a kettle and pour into the beakers
3. Record the initial temperature of the water in each beaker
4. Record how the temperature changes every few minutes

Give examples of materials with insulation properties that can be tested using this method.

● Newspaper
● Corrugated cardboard
● Bubble wrap
● Polystyrene
● Cotton wool
● Tin foil

How can you secure the materials once wrapped around the beaker?

Using rubber bands.

Why do you leave one beaker with no insulation wrapped around it?

To act as a control beaker. It can be used to compare the temperature drop of the water with and without insulation.

As well as wrapping the beaker with the insulation, what else should you do to insulate it?

Cut out a circle for the lid of the beaker to reduce heat loss from the top. The lid should have a small hole for the thermometer to fit into.

What readings do you take and how frequently?

You record the temperature of the water in fixed intervals of around 3 minutes.

How can you compare the effectiveness of the different insulators?

Compare the temperature change that has occured over a fixed interval of time. The smaller the temperature change, the more effective the insulator is.

As well as the effectiveness of different types of insulators, what else can you test using this method?

The effectiveness of different thicknesses of the same insulator.

What safety precautions should be taken when carrying out this experiment?

● Avoid touching the beaker after heating
● Place on a heatproof mat when hot
● Take care when pouring boiling water to avoid scolding
● If a beaker cracks, avoid using it and inform a technician

Outline the basic steps of the resistance practical.

1. Set-up circuit
2. Attach resistance wire to metre rule
3. Move the crocodile clip along the wire in increments, taking measurements for voltage and current each time
4. Calculate the resistance for each length

What two types of meters are needed in the circuit, and how should they be connected?

1. Voltmeter: Connected in parallel to the resistance wire
2. Ammeter: Connected in series with the resistance wire

What equation is used to obtain the resistance from the current and voltage readings?

R=V/I

What should the graph of resistance against length look like?

The two variables are directly proportional so should produce a straight line going through the origin.

In reality, why might the line produced not pass through the origin?

There may be a zero error. This may be because it is hard the attach the stationary crocodile clip exactly at the zero end of the metre rule.

Why should the wire used be thin?

● For a given material, the thinner the wire, the higher the resistance
● This makes the recorded resistance values large enough to be measured and interpreted

Why should a low potential difference be used when carrying out this experiment?

To prevent the current getting too high and the wire heating up.

What is the issue if the wire heats up during the experiment?

Resistance of a wire will increase if the temperature increases, creating an extra variable which will interfere with the results. Temperature should remain a control variable.

Why does resistance increase with temperature?

The metal ions have more kinetic energy so vibrate more. This causes them to collide more frequently with current-carrying electrons, providing more resistance against the flow of electrons.

What safety precautions should be taken when carrying out this experiment?

● Avoid touching the wire since it may be very hot
● Keep potential difference values low to avoid overheating

If both resistors are identical, which combination of resistors will have the least resistance?

The resistors in parallel will have a lower resistance than the resistors in series.

Relative to the resistance of the resistors, describe the total resistance of the parallel combination.

The total resistance will be lower than the resistance of the smallest of the two individual resistances.

Outline the basic steps of the IV characteristics practical.

1. Set-up circuit with lamp/resistor/diode
2. Alter the potential difference in regular increments
3. Record the current for each p.d
4. Plot a graph of current against p.d
5. Repeat for the other two components

What component is required to alter potential difference if you’re not using a variable power pack?

A rheostat, or variable resistor.

What is an ‘Ohmic Conductor’? State the condition required.

● A conductor for which current and potential difference are directly proportional
● Resistance remains constant as current changes
● Temperature must be constant

What specific type of ammeter may be required in this experiment and why?

A milliammeter since the currents and current changes involved may be quite low.

What must also be present in the circuit when the diode is being tested? Where should it be connected?

A protective resistor should be connected
to prevent the current levels getting too high. It should be connected in series with the diode.

For which component does the polarity of the power supply matter and why?

The diode, since diodes only allow current to flow through in one direction.

What must be kept constant to get reliable results? How can you achieve this?

Temperature should remain constant so that the resistance of the components isn’t affected. You should disconnect the supply when not taking readings to avoid unnecessary heating.

How do you determine the resistance of a component from an I-V graph?

The resistance at a given point, is the inverse of the gradient of the line drawn from that point to the origin. Work out the gradient and use 1/gradient to obtain the resistance.

What happens to the resistance of a filament lamp as the temperature increases? Why?

● Resistance increases
● Ions in metal have more energy, so vibrate more, causing more collisions with electrons as they flow through the metal, creating greater resistance to current flow

Outline the basic steps of the density of a regular shape practical.

1. Measure the dimensions of the regular shape and calculate the volume
2. Measure the mass of the shape using a calibrated balance
3. Calculate density from the mass and volume

Give the formula for the volume of a prism

Volume = area of face x height

Give the formula for the volume of a sphere

Volume = 4/3 x 𝜋 x radius³
V = 4/3𝜋r³

What unit is used for density?

kg/m³

What piece of equipment is used to measure the object’s mass? What must you do before using it?

A digital balance, which should be zeroed before placing the object on it to avoid a zero error.

How do you convert from g/cm³ to kg/m³?

Multiply the value by 1000.

Outline the basic steps of the density of irregular objects practical.

1. Measure the mass of the irregular shape
2. Fill a displacement can with water and submerge the object
3. Record the volume of water that has been displaced
4. Calculate the density from the mass and volume

What should you place under the can spout to collect the water?

A measuring beaker.

Explain how you should fill the displacement can to get the most accurate results.

Fill the can until water starts to drip out of
the spout and into the beaker. Wait until the dripping just stops before submerging the object.

Outline the basic steps of the density of a liquid practical.

1. Measure the mass of the empty measuring cylinder
2. Pour around 100cm³ of liquid into the cylinder and record the volume
3. Measure the mass of the cylinder with liquid in, and subtract the cylinder’s mass to calculate the mass of liquid.
4. Calculate density from mass and volume

How does the density of solids and liquids compare?

In general, solids are more dense than liquids since their particles are more tightly packed together meaning there is more mass per unit volume.

Outline the basic steps of the force and extension practical.

1. Hang a spring from a clamp stand alongside a metre rule
2. Measure the spring’s initial length
3. Add weights in intervals of 10N and record the extension
4. Plot a graph of extension against force

What piece of apparatus is used to secure the clamp stand to the desk and why?

● A G-Clamp, so that the clamp doesn’t tip over whilst adding masses
● The clamp produces a moment which counteracts the moment caused by the masses so the stand remains in equilibrium

How do you calculate the extension of the spring when you add masses?

Subtract the extended length of the spring from the original unstretched length.

What can you add to the spring to ensure that the extension measurements are accurate?

A pointer (eg. a splint) attached horizontally to the base of the spring and extending to the metre rule. This will make reading the length easier.

What piece of safety equipment should be used throughout this experiment and why?

Safety glasses should be worn in case of the spring breaking or becoming unattached and damaging your eyes.

What other safety precautions should be taken?

You should avoid standing with your feet underneath where the weights are hanging in case they fall, and wear appropriate footwear.

What graph should you plot with your results? What would you expect it to look like?

Extension against force (weight). You would expect it to be a straight line passing through the origin. The variables should be directly proportional.

What is the name of the relationship between extension and force?

Hooke’s Law.
Force = Spring Constant x Extension

What type of energy is stored in the spring as it is stretched?

Elastic Potential Energy

What equation can be used to calculate the elastic potential stored in the spring?

Elastic Potential Energy = 0.5 x Spring Constant x Extension²
E = ½kx²

How can the elastic potential stored in the spring be worked out graphically?

The stored energy is equal to the area under the force/extension graph.

How can you use your apparatus and graph to work out the weight of an unknown object?

1. Hang the object on the spring and record the extension it produces
2. Draw a line from that extension on your graph until it meets your plotted line and then read off the corresponding weight

Outline the basic steps of the effect of force on acceleration (with constant mass) practical.

1. Mark out 20 cm intervals on a bench using a ruler
2. Attach a string to the trolley, and pass it over a pulley at the end of the bench
3. Attach varying masses to the end of the string and release them so the trolley accelerates
4. Time how long it takes to reach each interval

Suggest a method for marking out 20cm intervals on the desk.

Place pieces of tape every 20cm from the starting point of the trolley. Use a metre rule to measure each interval.

What piece of equipment is used to record the times?

A stopwatch with the ability to record multiple times (laps) so you can record when it passes each interval.

What safety precautions should be taken when releasing the masses?

Ensure you are not standing underneath where they are hanging. A padded bucket could be placed underneath them to catch them when they drop.

How would you expect the acceleration of the trolley to change as you add more weights to the end of the spring?

The more weights that are added, the greater the force that is accelerating the trolley and so the greater the acceleration.

Which of Newton’s laws explains the relationship between force and acceleration? State the relevant equation.

Newton’s Second Law
Force = Mass x Acceleration

Outline the basic steps of the effect on mass on acceleration (with constant force) practical.

1. Mark out 20 cm intervals on a bench
2. Attach a string to the trolley, and pass it over a pulley at the end of the bench
3. Attach a fixed mass to the end of the string and release it so the trolley accelerates
4. Time how long it takes to reach each interval
5. Repeat with varying masses attached to the trolley

How can you choose an appropriate quantity of masses to use as the fixed mass for this experiment?

Carry out a preliminary experiment to find what weight is needed to just accelerate the trolley from rest.

What would be the consequence of using too large a fixed weight?

The trolley would accelerate too quickly for the timing at each interval to be accurate.

How would you expect the acceleration of the trolley to change when you add masses onto the trolley?

The acceleration will decrease as masses are added to the trolley, because a = F/m.

Suggest a way that the experiment could be changed to improve the timing of the trolley at each interval.

A video camera could be used to record the experiment and then timings taken from the slowed down video afterwards. This reduces uncertainty from human reaction times. Alternatively, light gates could be used.

What is a ripple tank?

A shallow glass tank with an oscillating paddle/needle to create waves. It is illuminated from above so the waves can be seen on the surface below the tank.

Outline the basic steps of the waves in liquids practical.

1. Set up the ripple tank with a lamp above it and white card/paper below it
2. Switch on the motor attached to the wooden rod
3. Measure the wavelength of the waves being cast onto the card
4. Count the number of waves passing a point in 10 seconds and calculate the frequency
5. Calculate the wave speed

Approximately how much water should you put into the ripple tank? What would the consequence of too much be?

The water should be poured to a depth of around 5 mm. If there is too much water the rod won’t produce clear waves and they will be less clearly projected onto the card below.

How should the wooden rod be set up in the ripple tank?

The wooden rod should be placed into the tank so that it just touches the surface of the water.

How should you measure the wavelengths of the waves on the card?

1. Adjust the lamp position so that the waves are clearly projected onto the card
2. Using a metre rule, measure across as many waves as you can
3. Divide the distance by the number of waves measured across

What units should your measured wavelength be in?

Metres, m.
(It may be easier to measure in cm, but wavelength must be in m for the wave equation).

Why should you measure across more than one
wave?

To reduce the uncertainty in the measurement and improve the accuracy of the value.

How do you measure the frequency of the waves on the card?

1. Count the number of waves passing a chosen point in 10 seconds
2. Divide the number by 10, to produce a frequency in Hz

What equation is used to calculate wave speed?

Wave Speed = Frequency x Wavelength

When the frequency is in Hertz and the wavelength is in metres, what is the unit for wave speed?

m/s
Metres per Second

Outline the basic steps of the waves in a solid practical.

1. Attach a piece of string to a vibration generator at one end and to a mass hanger suspended over a pulley at the other
2. Place the wooden bridge under the string before it reaches the pulley
3. Start the generator and alter the tension and bridge until it looks like the wave isn’t moving
4. Measure the wavelength, and record the frequency
5. Calculate wave speed

How do you measure the wavelength?

1. Using a metre ruler, measure across as many loops as you can
2. Each loop is a half wavelength
3. Divide the distance by the number of loops and multiply by two to get the wavelength

What value is used for the frequency?

The value should be taken from the frequency generator settings

Outline the basic steps of the light practical.

1. Draw a straight line and a line normal to it in the centre of the paper
2. Place the block along the main line and shine the ray light at the position where the normal meets the box
3. Mark with crosses the incoming, and any outgoing rays of light
4. Turn lights on and measure the angles of incidence, reflection and refraction

What tool should be used to help draw the normal line on the sheet of a paper?

A set square or protractor to ensure that the angle is at a right angle to the main line.

What precautions should be taken to use the ray box safely?

● Don’t touch any metal parts since the box gets very hot when in operation
● Switch off when not in use to prevent overheating

What conditions are needed for this experiment?

Low lighting is needed so that the rays are visible

What three angles should you measure after you have marked the lines on the paper? How?

1. Angle of incidence
2. Angle of reflection
3. Angle of refraction
   Using a protractor.

Which angle is the angle of incidence?

The angle as measured between the incident (incoming) ray and the normal.

Which angle is the angle of reflection?

The angle as measured between the reflected ray and the normal.