11 mark
An a.c. supply of negligible internal resistance is connected to a 39 Ω resistor. The r.m.s. voltage of the supply is 7·0 V. The peak power dissipated in the resistor is
Electricity · Practice Test B
Higher Physics · Electricity
Practice Test B
Answer everything, then mark it in one go.
45marks
60 minsuggested
14questions
Have your jotter and a pen beside you. Do every calculation in your jotter, showing the relationship, the substitution and the final answer with its unit, exactly as you would in the exam — this page asks you only for the relationship you used and your final answer.
Powers of ten can be typed any way you like — 2.5e4, 2.5*10^4, 2.5x10^4 or 2·5 × 10⁴ are all read the same.
Nothing is timed and nothing is sent anywhere — your answers stay on this device, so you can close the tab and come back.
Relationships you may need
| Quantity | Relationship |
|---|---|
| Peak and r.m.s. | Vpeak = √2 Vrms Ipeak = √2 Irms |
| Period and frequency | T = 1 / f |
| Charge and current | Q = It |
| Resistance and power | V = IR P = IV = I2R = V2 / R |
| Combining resistors | RT = R1 + R2 + … 1 / RT = 1 / R1 + 1 / R2 + … |
| E.m.f. and internal resistance | E = V + Ir |
| Potential divider | V1 = (R1 / (R1 + R2)) VS |
| Capacitance and energy stored | C = Q / V E = ½QV = ½CV2 = ½Q2 / C |
Working goes in your jotter. On this page you give the relationship and the final answer only — the mark scheme at the end shows the substitution you should have written down.
Warm-up
8 marksEveryone should aim for full marks here. One step, no rearranging.
21 mark
The output of a signal generator is displayed on an oscilloscope. The trace is shown. The Y-gain setting is 0·20 V/div. The r.m.s. voltage of the output is
31 mark
A circuit is set up as shown. The battery has negligible internal resistance. A student makes the following statements.
- When switch S is open, the reading on the voltmeter is 3·3 V.
- When switch S is closed, the reading on the ammeter is 0·30 A.
- Closing switch S increases the reading on the voltmeter.
41 mark
In each of the combinations shown, every resistor has the same resistance R. Which combination has the greatest effective resistance between X and Y?
51 mark
A cell of internal resistance 1·8 Ω is connected to a 8·2 Ω resistor as shown. The voltmeter is connected across the terminals of the cell. The switch is closed and the reading on the ammeter is 0·12 A. Which row shows the e.m.f. of the cell and the reading on the voltmeter?
61 mark
A 390 μF capacitor is connected to a 5·5 V d.c. supply of negligible internal resistance until it is fully charged. The energy stored in the capacitor is
71 mark
A capacitor is connected in the circuit shown. The battery has negligible internal resistance. The capacitor is initially uncharged, and the switch is then closed. When the reading on the voltmeter is 2·4 V, the charge stored on the capacitor is
81 mark
A student makes the following statements about semiconductors.
- In an n-type semiconductor, the majority charge carriers are electrons.
- When an LED is reverse biased, electrons fall from the conduction band to the valence band and emit photons.
- A p–n junction diode conducts when it is reverse biased.
Core
24 marksThe demand of the real test — one rearrangement, one conversion or one intermediate step.
96 marks
A student uses the circuit shown to investigate the battery of a head torch. When switch S is open, the reading on the voltmeter is 3·2 V. Switch S is closed: the reading on the voltmeter is now 2·6 V and the reading on the ammeter is 0·75 A.
(a) State the e.m.f. of the battery.1
(b) Calculate the internal resistance of the battery.3
(c) Explain why the reading on the voltmeter decreases when switch S is closed.2
107 marks
A student charges a capacitor fully from a d.c. supply and measures the charge stored with a coulombmeter. The student records a potential difference across the capacitor of 5·8 V and a charge of 2·61 mC.
(a) Calculate the capacitance of the capacitor.3
(b) The capacitor is discharged and connected in series with a 27 kΩ resistor and the supply. The time t taken for the capacitor to charge fully can be estimated using the relationship t = 5RC. Calculate the estimated time taken for the capacitor to charge fully.2
(c) The 27 kΩ resistor is replaced by one of greater resistance. State the effect this has on the time taken for the capacitor to charge fully. You must justify your answer.2
117 marks
An a.c. supply of negligible internal resistance, with a peak voltage of 11·3 V, is connected to a 330 Ω resistor and a 470 Ω resistor in series, as shown.
(a) Calculate the r.m.s. voltage of the supply.2
(b) Calculate the r.m.s. current in the circuit.3
(c) Calculate the mean power dissipated in the 470 Ω resistor.2
124 marks
The diagrams show the valence band and the conduction band of three materials. Shaded areas represent bands occupied by electrons.
(a) State which material is a semiconductor.1
(b) State which material is a conductor.1
(c) Using band theory, explain why the conductivity of the semiconductor increases as its temperature increases.2
Push
13 marksTwo or more steps, an unfamiliar context, and a judgement to justify.
138 marks
A cordless drill is powered by a battery pack of e.m.f. 14·4 V and internal resistance 0·050 Ω. While drilling, the motor has a resistance of 0·35 Ω.
(a) Calculate the current in the motor while drilling.3
(b) Calculate the power wasted in the internal resistance of the battery pack.3
(c) The drill bit jams in the wood, and the resistance of the motor decreases. Explain why the potential difference across the motor decreases.2
145 marks
An uncharged 270 μF capacitor is connected in the circuit shown. The 5·6 V battery has negligible internal resistance. Switch S2 is open.
(a) Switch S1 is closed. Calculate the initial charging current.3
(b) The capacitor is discharged. Switch S2 is now closed, and then switch S1 is closed. State the effect this has on the maximum charge stored on the capacitor. You must justify your answer.2
Your result
0out of 45
0%percentage
—indicative band
Bands are indicative only — they are a guide to where you are, not a grade.
Sources & credits: questions are adapted from Higher Physics past papers, reproduced and adapted for educational use — past papers and marking instructions © Qualifications Scotland (SQA). Numbers, circuits and contexts have been changed, and some questions are original to this site. Circuit diagrams, oscilloscope traces, graphs and band diagrams drawn for this site © R Stewart Physics, Electronics and Engineering, 2026.