Question

It is required to construct a transformer which gives 12 V from a 240 V AC supply.
The number of turns in the primary is 4800.
a) Calculate the number of turns in the secondary.
b) State whether, coil in the secondary has to be thick or thin. Justify your answer.

Answer 1

Given voltage generated by a transformer = 12 V
Number of turns in the primary coil = 4800
a) Let $V_s$ and $N_s$ be the voltage and the number of turns of the secondary coil of the transformer.
Let $V_p$ and $N_p$ be the voltage and the number of turns of the primary coil of the transformer.
We know that:
$\frac{V_s}{V_p}=\frac{N_s}{N_p}$
$\Rightarrow N_s=\frac{V_s}{V_p}\times N_p$
Given $V_s=12V,V_p=240V$
$N_s=?,N_p=4800$
Substituting the values we get:
$N_s=\frac{12}{240}\times 4800$
$N_s=240$ turns
The number of turns in the secondary coil is 240.
b) The coil in the secondary has to be thick because it is a step-down transformer. In a step-down transformer, thin wire is used in the primary coil, whereas thick wire is used in the secondary coil.A step-down transformer is used to change high-voltage alternating current to low-voltage alternating current. Such transformers are used for the distribution of electric power to homes.