Transformer

Question 1

State the definition of transformer.

A device that can ______ or ________ voltage of an _______ current using the principle of ____________

Answer 1

raise; lower; alternating ; electromagnetic induction

Question 2

A transformer is made up of _________ coiling around ________.

Answer 2

two coils ( Primary and secondary coil) 
soft iron core

Question 3

What is primary coil connected to? What is secondary coil connected to?

Answer 3

• primary coil connects to the alternating current

- secondary coil connects to the output terminals

Question 4

Why must we use alternating current instead of direct current?

Answer 4

• alternating current has an increase and decrease of magnetic flux
• resulting continuous cutting of magnetic flux

Question 5

Why does light bulb lights up the secondary coil when primary coil is connected to alternating current?

Answer 5

• cutting of magnetic flux
• produces induced emf
• resulting induce current

Question 6

Explain how a transformer works? ( 4 points)

Answer 6

1. the coil connected to alternating current is known as primary coil. The coil that is connected to light bulb is known as secondary coil
2. When alternating current flows through the coil, changing magnetic field will be produced
3. The magnetic field will be “ cut” through secondary coil hence alternating emf produced and current of same frequency will be induced into the coil
4. The magnitude of induced emf and current by the secondary coil depends on the number of turns in primary coil and secondary coil

Question 7

State the differences of step-up and step-down transformer.

Answer 7

Step up

• Increase voltage
• Coils of primary coil is more lesser than the coils of secondary coil
• current of primary coil< current of secondary coil
• example: X-ray, microwave over

Step down

• Decrease voltage
• Coils of primary coil is more that coils of secondary coils
• current of primary coil> current of secondary coil
• example: Laptop charger, photocopy machine

Question 8

What is the relationship between the number of coils and the voltage?

Answer 8

Vp Vs
______ = _______
Np Ns

Question 9

What is the relationship between the Voltage and curret?

Answer 9

VpIp- VsIs

Question 10

State the 4 factors that causes energy loss in transformer.

Answer 10

1. resistant of coil
2. hysteresis
3. eddy current
4. leakage of magnetic flux

Question 11

How does resistant of coil contribute in energy loss of transformer?

How to overcome it?

Answer 11

• long wires
• when current flow through wire for long period of time, heating of wire resulting heat energy loss
• use wire with larger diameter

Question 12

What is eddy current?

How to overcome it?

Answer 12

• useless current
• core is just a conductor, the changing of magnetic flux causes iron ore to possess induce current
• causing iron ore to generate heat
• Laminate iron core
• insulated with iron sheet
• energy loss is reduced

Question 13

What causes leakage of magnetic flux?

How to overcome it?

Answer 13

• magnetic flux produce by primary coil does not link with secondary coil
• Winding secondary coil on top of primary coil/ place close to each other
• to ensure more magnetic flux from primary coil can be cut by secondary coil

Question 14

What is hysteresis?

How to overcome it?

Answer 14

• Iron core is magnetize and demagnetize continuously by changing magnetic field
• energy supplied for magnetization is not fully recovered during demagnetization
• cause iron core to heat up
• use soft iron ore
• can be magnetize and demagnetize easily.