Force, Energy & Communication

Lesson 10 & 11

TRANSFORMERS

Lesson Objectives

Appreciate the role of transformers Understand how to make and use a

transformer To be distinguish between a step-up and

step-down transformer. To understand and be able to use the

transformer equation

NO! Not one of these!

That’s better, one of these!

PHYSICS TEXT BOOK

Turn to page 94

PHYSICS TEXT BOOK

Turn to page 94

Come round the front bench!

Really – they are just too camp!

Transformers

The job of a transformer is to change the voltage in a circuit.

Transformers

A step down transformer REDUCES the voltage in a circuit.

The input voltage is higher than the output voltage.

e.g. transformers found in electrical sub-stations

Transformers

A step up transformer increases the voltage in a circuit.

The input voltage is lower than the output voltage.

e.g. transformers used to convert USA voltage to UK voltage

What a transformer is made of Consists of two coils of wire wrapped around

a soft iron core. The coil attached to the INPUT voltage is

called the PRIMARY coil The coil attached to the OUTPUT voltage is

called the SECONDARY coil.

This is a STEP-UP transformer (more coils in the secondary than primary coil)

Collect an experiment sheet and carry out your own investigation into transformers.

Calculating the output voltage The output voltage can be calculated using

this formula:

Calculating the output voltage The output voltage can be calculated using

this formula:

secondary (output) voltage = no. of turns on secondary coil

primary (input) voltage no. of turns on primary coil

Worked example

A transformer has 960 turns on the primary coil and 16 turns on the secondary coil. The primary coil is connected to 230V a.c.. What will be the output?

Worked example

A transformer has 960 turns on the primary coil and 16 turns on the secondary coil. The primary coil is connected to 230V a.c.. What will be the output?

secondary voltage = 16

230 V 960

Worked example

A transformer has 960 turns on the primary coil and 16 turns on the secondary coil. The primary coil is connected to 230V a.c.. What will be the output?

secondary voltage = 16

230 V 960

So the secondary voltage = 230 X (16/960)

=

Worked example

A transformer has 960 turns on the primary coil and 16 turns on the secondary coil. The primary coil is connected to 230V a.c.. What will be the output?

secondary voltage = 16

230 V 960

So the secondary voltage = 230 X (16/960)

= 3.9 V

Collect “The transformer – data analysis”

Carry out all the exercises on this sheet.

Collect “The transformer – data analysis”

Carry out all the exercises on this sheet.

HW Complete the questions on the sheet

“TRANSFORMERS” – hand in on Thursday.

Lesson Objectives

Appreciate the role of transformers Understand how to make and use a

transformer To be distinguish between a step-up and

step-down transformer. To understand and be able to use the

transformer equation