The Physics Question Bank

Course: Combined Science + Separate Physics  |  Tier: Foundation + Higher  |  Equation sheet: given in the exam

The equation

potential difference = current × resistance    V = I R

Quantity	Symbol	Unit
potential difference	V	volts (V)
current	I	amperes (A)
resistance	R	ohms (Ω)

Rearranged: I = V ÷ R  |  R = V ÷ I  |  1 kΩ = 1000 Ω; 1 mA = 0.001 A

Use FIFA for every answer

• F – Formula: write the equation as it appears on the sheet.
• I – Insert: put in the numbers (convert to standard units first).
• F – Fix: rearrange to make the unknown the subject.
• A – Answer: calculate and always give the unit.

Foundation: aim for Q1–8.   Higher: aim for Q4–10. Most questions need rearranging.

---

Questions

Q1 (F) A current of 2 A flows through a 6 Ω resistor in a toy car. Calculate the potential difference across it.

Show solution

F: V = I R
I: V = 2 × 6
F: V is already the subject
A: 12 V

Q2 (F) A heater with a resistance of 46 Ω is connected to the 230 V mains. Calculate the current.

Show solution

F: V = I R
I: 230 = I × 46
F: I = 230 ÷ 46
A: 5 A

Q3 (F) A 9 V battery makes a current of 0.3 A flow through a lamp. Calculate the resistance of the lamp.

Show solution

F: V = I R
I: 9 = 0.3 × R
F: R = 9 ÷ 0.3
A: 30 Ω

Q4 (F) An LED needs a p.d. of 3.0 V and a current of 20 mA. Calculate its resistance.

Show solution

Convert first: 20 mA = 0.020 A
F: V = I R
I: 3.0 = 0.020 × R
F: R = 3.0 ÷ 0.020
A: 150 Ω

Q5 (F) A 2.0 kΩ resistor in a phone circuit has 12 V across it. Calculate the current in mA.

Show solution

Convert first: 2.0 kΩ = 2000 Ω
F: V = I R
I: 12 = I × 2000
F: I = 12 ÷ 2000 = 0.006 A
A: 6 mA

Q6 (F/H) A 6 Ω and a 4 Ω resistor are connected in series to a 5 V battery. Calculate the current.

Show solution

Total resistance in series: 6 + 4 = 10 Ω
F: V = I R
I: 5 = I × 10
F: I = 5 ÷ 10
A: 0.5 A

Q7 (F/H) A thermistor in a fridge sensor has a resistance of 1.5 kΩ. A current of 4 mA flows through it. Calculate the p.d. across it.

Show solution

Convert first: 1.5 kΩ = 1500 Ω; 4 mA = 0.004 A
F: V = I R
I: V = 0.004 × 1500
F: V is already the subject
A: 6 V

Q8 (F/H) Dry human skin can have a resistance of 1.0 × 10⁵ Ω. Calculate the current if someone touches a 230 V wire. Give your answer in standard form.

Show solution

F: V = I R
I: 230 = I × 1.0 × 10⁵
F: I = 230 ÷ 1.0 × 10⁵
A: 2.3 × 10⁻³ A

Q9 (H) 90 C of charge flows through a 20 Ω resistor in 30 s. Calculate the p.d. across the resistor.

Show solution

Step 1 – current
F: Q = I t
I: 90 = I × 30
F: I = 90 ÷ 30 = 3 A
Step 2 – p.d.
F: V = I R
I: V = 3 × 20
A: 60 V

Q10 (H) A 1.5 V AA cell makes a current of 0.28 A flow through a bulb. Calculate the bulb’s resistance, to 2 significant figures.

Show solution

F: V = I R
I: 1.5 = 0.28 × R
F: R = 1.5 ÷ 0.28
A: 5.357… = 5.4 Ω (2 s.f.)