O-LevelPhysicsMagnetism5054/21 · Oct/Nov 2020 · Q67 Marks

When electricity is transmitted over large distances, a transformer is used to increase the voltage before transmission. A second transformer is used at the destination to decrease the voltage to the usual mains value.

(a)Sketch a labelled diagram to show the structure of a transformer that is used to increase voltage.[2]
(b)Describe the principle of operation of a transformer.[3]
(c)Explain one advantage of transmitting electricity at a high voltage.[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

[B1] iron core and two coils wrapped around core
[B1] input and output clear and more turns on secondary / output coil
[B1] magnetic field mentioned
[B1] alternating current (a.c.) produces magnetic field that varies
[B1] core channels magnetic field to secondary coil and electromagnetic induction
[B1] less energy transferred to thermal energy in wires
[B1] (because) smaller current (for a given power)

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Topic: Magnetism, O-Level Physics (syllabus 5054). Structured question, 7 marks.
Source: O-Level Physics, Oct/Nov 2020 Paper 2 Variant 1, question 6.

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