AQA GCSE Physics Physics Paper 1 (Foundation), November 2020: Question 4
8 marks · Standard Demand difficulty · Short Answer
Analyze data from a practical investigation into the resistance of resistors connected in series, calculating mean resistance, resolution, precision, direct proportionality, predictions from a graph, and circuit behavior.
Practise this questionQuestion
Question text
04 A student investigated how the total resistance of identical resistors connected in
series varied with the number of resistors.
The student used an ohmmeter to measure the total resistance of the resistors.
Figure 6 shows the student’s circuit with 3 resistors.
Figure 6
The student repeated each reading of resistance three times.
Table 1 shows the student’s results for 3 resistors in series.
Table 1
Number of Total resistance in Ω
resistors
Reading 1 Reading 2 Reading 3 Mean
3 35.9 36.0 36.1 36.0
04.1 Calculate the mean resistance of 1 resistor.
[2 marks]
Resistance = Ω
04.2 What was the resolution of the ohmmeter the student used?
Tick ( ) one box.
[1 mark]
0.1 Ω 0.2 Ω 13 1.1 Ω 36.0 Ω
04.3 How do the results show that the student’s measurements were precise?
[1 mark]
Tick ( ) one box.
The measurements are accurate.
The measurements are grouped closely together.
The measurements are reproducible.14
Figure 7 shows the results.
Figure 7
04.4 How do the results show that the total resistance is directly proportional to the number
of resistors?
[1 mark]
Tick ( ) one box.
The results give a line with a positive gradient.
The results give a straight line that would go through the origin.
*13* The results show a linear relationship.
04.5 Predict the mean total resistance of 7 resistors.
Use Figure 7.
[1 mark]
Mean total resistance of 7 resistors = Ω
*0144*6
. Some resistors are connected in series with a battery.
When more resistors are added in series, the total resistance increases.
Complete the sentences.
Choose answers from the box.
Each answer may be used once, more than once or not at all.
[2 marks]
decreases increases remains the same
When the number of resistors increases, the potential difference across each
resistor .
When the number of resistors increases, the current in the
circuit .
Mark scheme
Show the mark scheme
Question 4
AO /
Question Answers Extra information Mark
Spec. Ref.
04.1 36.0 1 AO2
R = 4.2.2
RPA 3
R = 12.0 (Ω) 1
04.2 0.1 Ω 1 AO3
4.2.2
RPA 3
04.3 The measurements are grouped 1 AO3
closely together 4.2.2
RPA 3
04.4 The results give a straight line 1 AO2
that would go through the origin. 4.2.2
RPA 3
04.5 84 (Ω) allow an answer between 83 1 AO3
and 85 (Ω) inclusive 4.2.2
RPA 3
04.6 decreases 1 AO1
4.2.2
decreases 1 RPA 3
Total 8
How to answer it
Resistance of Resistors in Series Investigation
What this question tests
This question assesses your understanding of series circuits, required practical techniques (measuring resistance), data analysis skills (calculating means, determining resolution, assessing precision), interpreting graphical data (direct proportionality and interpolation), and applying qualitative rules about potential difference and current in series circuits.
Calculating the Mean Resistance of a Single Resistor
✅ Correct Answer
Resistance = 12.0 ohms
📐 Step-by-Step Calculation
- Identify the total mean resistance for 3 identical resistors from Table 1: 36.0 ohms .
- Set up the equation to find the resistance of just 1 resistor: R = 36.0 / 3
- Calculate the result: 12.0 ohms .
❌ Common Errors
- Forgetting to include the decimal place (writing 12 instead of 12.0 to match the table's significant figures).
- Multiplying instead of dividing by 3.
Determining Ohmmeter Resolution
✅ Correct Answer
Tick box: 0.1 ohms
💡 Key Knowledge
Resolution is the smallest change in a quantity that a measuring instrument can detect. Looking at Table 1, the readings change in increments of 0.1 ohms (e.g., 35.9, 36.0, 36.1), which tells us the resolution of the meter.
Identifying Precision from Data
✅ Correct Answer
Tick box: The measurements are grouped closely together.
💡 Key Knowledge
Precision refers to how close repeated measurements are to each other (repeatability). The three readings (35.9, 36.0, 36.1) span a very narrow range of just 0.2 ohms, showing high precision.
Recognising Direct Proportionality on Graphs
✅ Correct Answer
Tick box: The results give a straight line that would go through the origin.
🧠 Exam Technique
Students often confuse a positive gradient or a linear relationship with direct proportionality. For two variables to be directly proportional, the line must be straight and pass through the exact origin (0, 0).
Predicting Values from a Line Graph
✅ Correct Answer
84 ohms (Acceptable range: 83 ohms to 85 ohms inclusive)
🧠 Exam Technique
Go to 7 on the horizontal axis (number of resistors), move straight up to line up with the line of best fit in Figure 7, then read across to the vertical axis. Always use a ruler in exams to avoid parallax errors when reading graphs!
Series Circuit Rules (Current and Potential Difference)
✅ Correct Answer
- When the number of resistors increases, the potential difference across each resistor decreases.
- When the number of resistors increases, the current in the circuit decreases.
💡 Key Knowledge
- Total Resistance: Adding resistors in series increases total resistance ( R_total = R_1 + R_2 + ... ).
- Current: As total resistance increases, total current in the loop decreases ( I = V / R ).
- Potential Difference: The supply voltage is shared between the resistors. More resistors sharing the same supply means each individual resistor gets a smaller share of the potential difference.
Topics
Physics · Required Practicals · P2: Electricity · Required Practicals
Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 1 (Foundation), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.