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The transformer equation
1. A step-up transformer has a primary coil with 100 turns. It transforms the mains voltage of 230
V ac to 11 500 V ac.
(a)
How many turns must there be on the secondary coil?
(b)
When the current in the secondary coil is 0.10 A, what is the current in the primary coil?
2. A small power station generates 2 MW of electrical energy. How much power is lost in cables of
resistance 2 Ω if the electricity is transmitted at:
(a)
40 kV
(b)
4 kV
3. A transformer has a primary coil of 5000 turns. When the output pd is 12 V rms, the input pd is
240 V rms.
(a)
How many turns are there on the secondary coil?
(b)
The output from the secondary coil is connected across a 20 Ω lamp.
I.
What is the rms current in the secondary coil?
II.
What is the rms current in the primary coil?
III.
What assumption have you made?
