State the definition of transformer.
A device that can ______ or ________ voltage of an _______ current using the principle of ____________
raise; lower; alternating ; electromagnetic induction
A transformer is made up of _________ coiling around ________.
two coils ( Primary and secondary coil) soft iron core
What is primary coil connected to? What is secondary coil connected to?
- primary coil connects to the alternating current
- secondary coil connects to the output terminals
Why must we use alternating current instead of direct current?
- alternating current has an increase and decrease of magnetic flux
- resulting continuous cutting of magnetic flux
Why does light bulb lights up the secondary coil when primary coil is connected to alternating current?
- cutting of magnetic flux
- produces induced emf
- resulting induce current
Explain how a transformer works? ( 4 points)
- the coil connected to alternating current is known as primary coil. The coil that is connected to light bulb is known as secondary coil
- When alternating current flows through the coil, changing magnetic field will be produced
- The magnetic field will be “ cut” through secondary coil hence alternating emf produced and current of same frequency will be induced into the coil
- The magnitude of induced emf and current by the secondary coil depends on the number of turns in primary coil and secondary coil
State the differences of step-up and step-down transformer.
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
What is the relationship between the number of coils and the voltage?
Vp Vs
______ = _______
Np Ns
What is the relationship between the Voltage and curret?
VpIp- VsIs
State the 4 factors that causes energy loss in transformer.
- resistant of coil
- hysteresis
- eddy current
- leakage of magnetic flux
How does resistant of coil contribute in energy loss of transformer?
How to overcome it?
- long wires
- when current flow through wire for long period of time, heating of wire resulting heat energy loss
- use wire with larger diameter
What is eddy current?
How to overcome it?
- 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
What causes leakage of magnetic flux?
How to overcome it?
- 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
What is hysteresis?
How to overcome it?
- 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.
