Pearson Edexcel International GCSE (9–1) · PHYSICS · Chapter
Electromagnetic Induction
61 practice questions
Topics covered
Practice questions
31–40 of 61
Question 31
3 marks · Normal
Answer and see the solution →A transformer has an input voltage of 240 V and an input current of 0.50 A. The transformer is 100% efficient. The output voltage is 12 V.
(a)[3 marks]Calculate the current in the output circuit.
Question 32
2 marks · Normal
Answer and see the solution →A student suggests using a transformer with a direct current (d.c.) supply.
(a)[2 marks]Explain why a transformer does not work with d.c.
Question 33
3 marks · Normal
Answer and see the solution →A step-down transformer has a primary input voltage of 120 V and a primary input current of 0.25 A. The transformer is 100% efficient, and the output voltage is 24 V. Calculate the output current of the transformer.
Question 34
2 marks · Normal
Answer and see the solution →Explain why it is important for a transformer to be as efficient as possible when transmitting electricity over long distances.
Question 35
4 marks · Normal
Answer and see the solution →(a)[3 marks]A transformer is used to provide power to a small electronic device. The input voltage is 230 V and the input current is 0.080 A. The transformer is 100% efficient. The output current is 0.46 A.
Calculate the output voltage.
(b)[1 mark]State the formula used for your calculation.
Question 36
3 marks · Normal
Answer and see the solution →(a)[1 mark]State the meaning of 100% efficiency in a transformer.
(b)[2 marks]A transformer has an efficiency of 100%. The secondary coil provides an output power of 60 W. What is the input power?
Question 37
3 marks · Normal
Answer and see the solution →Describe two design features that help real transformers approach 100% efficiency. For each feature, briefly explain how it reduces energy losses.
Question 38
1 mark · Normal
Answer and check →A transformer has an input power of 75 W. Assuming 100% efficiency, which one of the following is the output power?
- A.50 W
- B.60 W
- C.75 W
- D.150 W
Question 39
4 marks · Normal
Answer and see the solution →(a)[3 marks]The table below shows input and output voltages and currents for three different transformers, each operating at 100% efficiency. Transformer Vp (V) Ip (A) Vs (V) Is (A) X 120 0.25 12 Y 240 0.15 48 Z 110 1.0 22 Complete the table by calculating the missing output current (Is) for each transformer.
(b)[1 mark]Explain briefly how you calculated the output current for transformer X.
Question 40
3 marks · Normal
Answer and see the solution →A transformer used in a mobile phone charger has an input voltage of 220 V and input current of 0.05 A. If the transformer is 100% efficient and the output power required is 8.8 W, what is the output current?