Boss Fight Quiz
4.5.6 Transformers - Comprehensive Assessment
Total Marks: 43 | Time: 45 minutes (suggested)
Exam Structure
Section A: Paper 2 (MCQ) - 5 questions - 5 marks
Section B: Paper 4 (Structured Theory) - 5 questions - 20 marks
Section C: Paper 6 (Practical Analysis) - 5 questions - 18 marks
⚠️ Examiner's Key Reminders
✓ Transformers only work with alternating current (a.c.)
✓ Step-down: Ns < Np, Step-up: Ns > Np
✓ For 100% efficiency: IpVp = IsVs
✓ High voltage transmission reduces power loss via P = I²R
Paper 2: MCQ[1 mark]
Q1. A transformer has a primary coil with 100 turns and a secondary coil with 50 turns. What type of transformer is this?
Paper 2: MCQ[1 mark]
Q2. Why is the core of a transformer made from soft iron rather than steel?
Paper 2: MCQ[1 mark]
Q3. What type of current is required for a transformer to operate?
Paper 2: MCQ[1 mark]
Q4. A transformer has 200 turns on the primary coil and 50 turns on the secondary coil. If the primary voltage is 240V, what is the secondary voltage?
Paper 2: MCQ[1 mark]
Q5. Which statement about high-voltage transmission of electricity is correct?
Paper 4: Structured[4 marks]
Q6. A transformer has an input voltage of 240V and an output voltage of 12V. The transformer has 100% efficiency. If the output current is 2A, calculate the input current.
Paper 4: Structured[4 marks]
Q7. Explain, using the equation P = I²R, why electricity is transmitted at high voltage to reduce power loss in cables.
Paper 4: Structured[4 marks]
Q8. A step-up transformer has 100 turns on the primary coil and 500 turns on the secondary coil. The primary voltage is 12V. Calculate the secondary voltage.
Paper 4: Structured[4 marks]
Q9. Explain the principle of operation of a transformer, describing how an alternating current in the primary coil produces a voltage in the secondary coil.
Paper 4: Structured[4 marks]
Q10. A transformer is used to step down 230V mains supply to 6V for a laptop charger. The secondary coil has 30 turns. Calculate the number of turns required on the primary coil.
Paper 6: Practical[3 marks]
Q11. A student investigates how the output voltage of a transformer varies with the number of turns on the secondary coil. The graph shows the student's results.
(a) Describe the relationship shown by the graph. [1 mark]
(b) The primary coil has 200 turns and is connected to a 12V supply. Use the graph to determine the number of secondary turns needed to produce an output voltage of 18V. [2 marks]
Paper 6: Practical[6 marks]
Q12. A student sets up the transformer circuit shown below to measure efficiency.
(a) State what measurements the student needs to take to calculate the efficiency of the transformer. [2 marks]
(b) The student measures Vp = 12V, Ip = 0.5A, Vs = 6V, Is = 0.9A. Calculate the efficiency of the transformer. [4 marks]
Paper 6: Practical[2 marks]
Q13. State TWO safety precautions that should be taken when working with transformers connected to mains voltage in a school laboratory.
(a) Precaution 1: [1 mark]
(b) Precaution 2: [1 mark]
Paper 6: Practical[4 marks]
Q14. A student investigates the effect of core material on transformer efficiency by using different cores.
(a) State ONE variable that must be kept constant in this investigation. [1 mark]
(b) Suggest why soft iron cores produce higher efficiency than air cores. [3 marks]
Paper 6: Practical[3 marks]
Q15. The diagram shows a transformer with a voltmeter connected across the secondary coil. The reading on the voltmeter fluctuates.
(a) Suggest ONE reason why the voltmeter reading might fluctuate. [1 mark]
(b) The student repeats each reading three times and calculates a mean. Explain why this improves the reliability of the results. [2 marks]
Quiz Complete?
🎯 Examiner's Final Tips
Formula Triangle: Know Vp/Vs = Np/Ns and IpVp = IsVs (100% efficiency)
Common Trap: Students confuse step-up with step-down. Remember: step-UP means voltage goes UP, so Ns > Np
Power Loss: Always explain using P = I²R when discussing transmission. The squared term is crucial
Keywords: Use "electromagnetic induction," "changing magnetic field," "soft iron core," "easily magnetized"
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