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Generation of Electrcity - Formal Homework 2: Transformers
A transformer consists of three parts.
(a) Identify each of the three parts on the diagram using the names below:
secondary coil
primary coil
(b) A power station generating electricity at 16 000 volts is connected by a
transformer to
the National Grid where the electricity is distributed around
the country at 275 000 volts
What is the name given to this type of transformer?
(c) The transformer has 18 000 turns on the primary coil.
Calculate the number of turns on the secondary coil.
A student has two electrical power supplies. One is an a.c. supply and the other is a
d.c supply.
Explain a.c and d.c in terms of electron flow in a circuit.
The student uses one of the supplies to operate a transformer.
Which power supply should be used to operate the transformer?
What is the purpose of a transformer?
(iii) A transformer with an efficiency of 30% is used in a computer.
Calculate the output power when the input power is 50 W.
In a lab experiment a technician builds a transformer and uses electrical meters to
take a number of measurements, as shown in the diagram:
The technician has a choice of an a.c. or a d.c. power supply. Which power
supply should be used?
Explain your answer.
Calculate the electrical power in the primary circuit of the transformer.
Calculate the electrical power in the secondary circuit of the transformer. 3
Calculate the percentage efficiency of the transformer.
Another experiment uses a different transformer. It is 100% efficient. The
primary coil has 15000 turns and the secondary coil contains 3000 turns.
Calculate the secondary voltage when the primary voltage is 12 V.
Total (21)