Question

The transformation ratio of a transformer is 10:1. The current in the primary circuit if the secondary current required is 100 A assuming the transformer be ideal, is
(A) 500 A
(B) 200 A
(C) 1000 A
(D) 2000 A

Answer 1

Hint
As the transformer is basically a linear device, a ratio now exists between the number of turns of the primary coil divided by the number of turns of the secondary coil. This ratio, called the ratio of transformation, more commonly known as a transformers “turns ratio”

Complete step by step answer
Let, the number of turns of secondary in $N_s$ and number of turns of primary in $N_p$.
We know, $N_s$ : $N_p$ = 10 : 1
According to the question current in secondary Is = 100 A
We know the relation between number of turns and current is
$ \Rightarrow \dfrac{{{N_S}}}{{{N_P}}} = \dfrac{{{V_S}}}{{{V_P}}} = \dfrac{{{I_P}}}{{{I_S}}}$.......equation 1
From this equation we can say,
$\begin{gathered}
   \Rightarrow \dfrac{{{N_S}}}{{{N_P}}} = \dfrac{{{I_P}}}{{{I_S}}} \\
   \Rightarrow {I_P} = \dfrac{{{N_S}{I_S}}}{{{N_P}}} \\
\end{gathered} $
Put the values given in the question,
$\begin{gathered}
  {I_P} = \dfrac{{10}}{1} \times 100 \\
  \therefore {I_P} = 1000A \\
\end{gathered} $
So, the current in primary is = 1000 A.
Option (C) is correct.

Note
A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. It can be designed to "step up" or "step down" voltages and works on the magnetic induction principle. A voltage is then induced in the other coil, called the secondary or output coil.