alternating-currents Question 38
Question: Q. 4. (i) Draw a labelled diagram of a step-up transformer. Obtain the ratio of secondary to primary voltage in terms of number of turns and currents in the two coils.
(ii) A power transmission line feeds input power at $2200 \mathrm{~V}$ to a step-down transformer with its primary windings having 3000 turns. Find the number of turns in the secondary to get the power output at $220 \mathrm{~V}$.
U] [Delhi I, III 2017]
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Solution:
Ans. (i) Labelled diagram of a step up transformer $1 \frac{1}{2}$ Derivation of ratio of secondary and primary voltage
(ii) Calculation of number of turns in the secondary.
(i) Try yourself, Similar to Q. 1 (a) Long Answer Type Questions.
(ii)
$$ \begin{align*} \frac{N_{s}}{N_{p}} & =\frac{V_{s}}{V_{p}} \tag{1/2}\ \frac{N_{s}}{3000} & =\frac{220}{2200} \end{align*} $$
$$ \therefore \quad N_{s}=300 $$
[CBSE Marking Scheme 2017]
