Physics · Edexcel 9PH0 · Paper 3: General and Practical Principles in Physics · November 2021
The length l of wire in the magnetic field was 15.5 cm. When the current in the circuit was 4.55 A, the reading on the balance increased by 5.65 g.
Calculate the magnetic flux density B in the region of the rigid wire.
(3)
The student wrote the following statement
“The balance could read to the nearest 0.01 g, which makes my values for the magnetic force both accurate and precise.”
Comment on this statement.
(3)
A student used a Geiger-Müller (GM) tube to determine the activity of a radium source. Radium emits α, β, and γ radiation.
He positioned the source 20 cm from the GM tube, as shown, and recorded the count for 1 minute. He repeated the measurement and calculated a mean count.
The student recorded the following results.
| Count 1 | Count 2 | Mean count |
| 183 | 178 | 181 |
Criticise the student’s method for determining the count at this position.
(3)
From his results the student determined that the activity of the source was 3.0 Bq.
Comment on his value for the activity of the source.
(5)
Genuine crystal balls are made from clarified quartz rather than glass. A student was given a small crystal ball and wanted to know whether it was genuine.
The mean diameter of the crystal ball was measured to be 5.06 cm and the mass of the crystal ball was measured to be 175 g.
Show that the density of the material of the crystal ball is about 2600 kg m−3.
(3)
The student measured the diameter of the crystal ball using vernier calipers with a resolution of 0.01 cm. She measured the mass of the crystal ball using a balance with a resolution of 1 g.
The table gives the densities of clarified quartz and glass.
| Material | Density / kg m−3 |
| Clarified quartz | 2650 |
| Glass | 2590 |
Determine whether the crystal ball was genuine.
(6)
Radioactive decay is often described in textbooks as a spontaneous, random process.
State what is meant by spontaneous decay.
(1)
*(b) Explain why there is an exponential decrease in the rate of decay for a sample containing a large number of unstable nuclei.
(6)
A student measured the height h of a liquid column in a capillary tube. She used a travelling microscope to make measurements of the positions of the top and bottom of the liquid column.
The travelling microscope consists of a simple microscope that can be moved vertically along a vernier scale.
The student used a capillary tube with an internal radius r equal to 0.10 mm and recorded the following readings from the vernier scale.
| Bottom of liquid column / cm | Top of liquid column / cm |
| 12.00 | 27.10 |
State the uncertainty in each of these readings.
(1)
Calculate the percentage uncertainty in the student’s value of h.
(2)
The student repeated the measurement of h for capillary tubes of different radii.
The table shows the student’s final data.
| r / mm | 1/r | h / cm |
| 0.09 | 11.1 | 16.56 |
| 0.10 | 10.0 | 15.1 |
| 0.12 | 8.3 | 12.6 |
| 0.15 | 6.7 | 10.33 |
Criticise the student’s recording of the data.
(2)
The student plotted the following graph.
Determine the height of the liquid column that the student could expect for a tube with an internal radius of 0.11 mm.
(3)
In her notes it stated that
Assess the extent to which the student’s data supports this relationship.
(4)
The Enterprise is an amusement park ride. Riders sit in cars that are made to rotate in a vertical circle.
The ride starts by moving in a horizontal circle. The speed of rotation increases, and the frame tilts until the ride is rotating vertically as shown.
The photograph below shows riders at the top of the vertical circle. The riders are in contact with their seats at all times during the ride.
The diagram shows the weight W of a rider and the push P from the seat on the rider at the top and bottom of the circular path.
*(a) The rider moves from the bottom to the top of the circular path.
Explain how the apparent weight experienced by the rider would change.
(6)
On the website of the amusement park it states
“The ride is perfectly safe without the need for safety harnesses for the riders. Centrifugal force ensures that the riders remain in their seats at all stages in the ride.”
Assess the validity of this statement.
(4)
A student connected the output from a source of alternating potential difference (p.d.) to a series resistor combination.
She connected an oscilloscope across the 150 Ω resistor as shown.
The trace obtained on the oscilloscope is shown below.
Determine the peak p.d. across the 150 Ω resistor.
y-sensitivity of oscilloscope = 2.0 V per division
Peak p.d. across 150 Ω resistor =........
(2)
Calculate the root mean square (r.m.s.) value of the current in the circuit.
r.m.s. value of current =........
(3)
Calculate the power dissipated in the circuit.
(3)
Another student suggested that a voltmeter would be more accurate than using an oscilloscope to determine the magnitude of the p.d.
Comment on this suggestion.
(3)
The apparatus shown can be used to determine a value for the specific latent heat of vaporisation of water.
In one experiment the current in the heater was 8.20 A, and the potential difference across the heater was 230 V.
Show that the power of the heater was about 2 kW.
(2)
There was 0.655 kg of water in the flask at an initial temperature of 22.5 °C. The heater was switched on, and the water in the flask was heated to boiling point.
Calculate the minimum time taken for the water to be heated to 100.0 °C.
specific heat capacity of water = 4190 J kg−1K−1
(3)
The heater was left on and water continued to boil in the flask. The water was allowed to boil for a few minutes. The conical flask was then placed under the heat exchanger and water was collected in it.
Give a reason why the water was left boiling for a few minutes before the conical flask was put in place.
(1)
Water with a mass of 95.0 g was collected in a time of 125 s.
Calculate the rate of energy transfer in the heat exchanger.
specific latent heat of vaporisation of water = 2.26 × 106J kg−1
(3)
Discuss your answers to (a)(i) and (b)(ii).
(3)
State how the apparatus could be modified to minimise the effect of a significant source of error.
(1)
A Hertzsprung-Russell (HR) diagram shows how the luminosity L depends on the surface temperature T for a group of stars.
The HR diagram below is for a young star cluster.
Explain how we can tell that the young star cluster is in the early stages of its evolution.
(2)
Explain why the most massive stars in the cluster have the greatest luminosities.
(4)
The HR diagram on the previous page shows an approximately linear relationship for stars in this cluster.
It is suggested that the relationship between luminosity L and surface temperature T is of the form
where k and n are constants.
Explain why a graph of log L against log T would give a straight line.
(2)
The table shows data for stars in this cluster.
Plot a graph of log L against log T on the grid opposite. Use the columns provided to show any processed data.
(5)
A student investigated the behaviour of a spring under tension. The spring was hung vertically with a mass holder attached as shown.
The student measured the length of the spring as he added masses to the holder. The rule was held as shown to measure the distance between the top and bottom coils of the spring. He determined the extension for each value of total mass on the holder. He did this by subtracting the original length of the spring from each extended length.
Explain whether this method would produce accurate values for the extensions of the spring.
(4)
Explain how the student could modify his method in order to obtain more accurate values for the extensions of the spring.
(5)
In another experiment, the student displaced the mass vertically each time a mass was added to the spring. He used a stopwatch to determine the period of vertical oscillations of each mass.
The student used his data to plot a graph of T2 against m as shown.
The student expected the graph to be a straight line through the origin. He thought that there may be systematic error due to reaction time.
Give an example of another possible systematic error in this experiment.
(1)
Another student suggests that to reduce the uncertainty in the value for the period, a data logger connected to a light gate could be used to measure time.
Comment on the student’s suggestion.
(3)
Determine a value for the stiffness of the spring.
(3)
When determining the period of oscillation for each mass, the student measured the time for 20 oscillations. He repeated this measurement to obtain a mean time for 20 oscillations.
Explain how the student’s procedure contributed to the accuracy of the measurement.
(3)
Light from a laser pointer was passed through a diffraction grating. The light was perpendicular to the diffraction grating as shown. A diffraction pattern was produced on
The distance between the first order maximum and the central maximum of the diffraction pattern was x. The distance between the diffraction grating and the screen was D.
Distance x was measured to be 0.500 m with a metre rule. The wavelength of light λ1 from the laser pointer was 650 nm. The laser pointer was replaced with one that produced light of a different wavelength. The new distance x was measured to be 0.400 m.
D = 1.45 m
Calculate the wavelength λ2 of the light emitted by the replacement laser pointer.
(5)
Explain one modification to this method that would decrease the uncertainty in the
(2)
In another experiment, the light from the laser pointer was not quite perpendicular to the screen.
Explain how this would change the diffraction pattern produced on the screen.
(3)
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