Describe how a transformer works.

An alternating current in the primary coil produces a continually changing magnetic flux in the iron core, and that changing flux linkage induces an alternating e.m.f. in the secondary coil.

Why will a transformer not work on direct current?

A steady current gives a steady flux, so there is no rate of change of flux linkage and no e.m.f. is induced in the secondary.

Give the transformer equation and define each symbol.

Vs/Vp = Ns/Np, where Vs and Vp are the secondary and primary voltages and Ns and Np the numbers of turns on the secondary and primary coils.

What is the purpose of the soft iron core?

It concentrates the magnetic flux so that almost all of the flux produced by the primary passes through the secondary.

CCEA A-Level Physics 1210

Physical Quantities, Scalars and Vectors

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Linear Motion and Dynamics

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Waves

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Quantum Physics

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Deformation of Solids

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Thermal Physics

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Uniform Circular Motion

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Simple Harmonic Motion

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The Nucleus and Radioactive Decay

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Gravitational Fields

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Capacitors

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Magnetic Fields

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Fundamental Particles

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Magnetic Fields

Transformers

3 things to know
Unit A2 2

Overview

How a transformer works, step-up transformer and step-down transformer.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is a step-up transformer?

Key term

What is a step-down transformer?

Key term

State the current relationship for an ideal transformer.

Questions from this subtopic

Each one with the model answer underneath.

1
Describe how a transformer works.
Model answer
An alternating current in the primary coil produces a continually changing magnetic flux in the iron core, and that changing flux linkage induces an alternating e.m.f. in the secondary coil.
2
Why will a transformer not work on direct current?
Model answer
A steady current gives a steady flux, so there is no rate of change of flux linkage and no e.m.f. is induced in the secondary.
3
Give the transformer equation and define each symbol.
Model answer
Vs/Vp = Ns/Np, where Vs and Vp are the secondary and primary voltages and Ns and Np the numbers of turns on the secondary and primary coils.
4
What is a step-up transformer?
Model answer
One with more turns on the secondary than the primary, so the secondary voltage is greater than the primary voltage.
5
What is a step-down transformer?
Model answer
One with fewer turns on the secondary than the primary, so the secondary voltage is lower than the primary voltage.
6
What is the purpose of the soft iron core?
Model answer
It concentrates the magnetic flux so that almost all of the flux produced by the primary passes through the secondary.

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