F - Transformers - Paper 2

Question 1

What is the purpose of a transformer?

Answer 1

Transformers are devices that convert electricity from one voltage to another through electromagnetic induction.

Question 2

What does a transformer consist of?

Answer 2

two solenoids (coils) and a soft magnetic material (iron core) and an ac (alternating current supply)

Question 3

Explain the use of step up and step down transformers in the transmission of electricity.

Answer 3

Electricity from a power station passes through a step up transformer. This increases the voltage but decreases the current. This saves energy losses in the cables due to heating of the metal cables. The transmitted electrcity passes through a step down transformer which decreases the voltage but increases the current before it reaches the industrial or domestic users.

Question 4

What is the transformer equation?

Question 5

A transformer has 4000 turns on the primary coil and 1000 on the secondary. The input voltage is 5V. Calculate the output voltage.

Answer 5

1.25V

Question 6

A transformer needs to output a voltage of 24v for an input voltage of 240v. The primary coil has 600 turns. How many does the secondary coil have?

Answer 6

60

Question 7

A transformer has 15000 turns on the primary coil and 5000 on the secondary. The input voltage is 20v. Calculate the output voltage.

Answer 7

6.67V

Question 8

A transformer needs to output a voltage of 40v for an input voltage of 800v. The primary coil has 4000 turns. How many does the secondary coil have?

Answer 8

200

Question 9

A transformer has 1000 turns on the primary coil and 200 turns on the secondary coil. If a voltage of 250V is applied to the primary coil, what is the voltage across the secondary coil?

Answer 9

50V

Question 10

What is the transformer efficiency equation?

Answer 10

input power = output powerorVP IP = Vs Is

Question 11

A transformer has an input current of 0.4A at a voltage of 240v. The output voltage is 12v. Calculate the output current.

Answer 11

8A

Question 12

A transformer has an output current of 0.1A at a voltage of 6000v. The input current is 6A. Calculate the input voltage.

Answer 12

100V

Question 13

A transformer has an input current of 0.02A at a voltage of 230v. The output voltage is 10v. Calculate the output current.

Answer 13

0.46A

Question 14

A transformer has an output current of 0.003A at a voltage of 25000v. The input current is 15A. Calculate the input voltage.

Answer 14

5V

Question 15

What is produced when a magnet moves in a coil of wire?

Answer 15

A voltage

Question 16

What do transformers change?

Answer 16

Alternating voltage

Question 17

What is the name given to a transformer that increases voltage

Answer 17

a step up transformer

Question 18

What is the name given to a transformer that decreases voltage

Answer 18

step down transformer