This question was previously asked in

UP TGT Science 2019 Official Paper

Option 1 : 5 A

CT 1: हिन्दी (आदिकाल)

6301

10 Questions
40 Marks
10 Mins

__Concept__:

- Transformer: An electrical device that is used to transfer electrical energy from one electrical circuit to another is called a transformer.
- In a transformer, there are two coils- The primary coil (P) and secondary coil (S).

There are two types of transformer:

- Step-up transformer: The transformer which increases the potential is called a step-up transformer.
- The number of turns in the secondary coil is more than that in the primary coil.

- Step-down transformer: The transformer which decreases the potential is called a step-down transformer.
- The number of turns in the secondary coil is less than that in the primary coil

In a transformer, the voltage in secondary is calculated by:

\(\frac{N_{s}}{N_{p}}=\frac{V_{s}}{V_{p}}=\frac{I_{p}}{I_{s}}\)

Here, Np and Ns are the numbers of turns in the primary and the secondary coils respectively and Vp and Vs are the RMS voltages across the primary and secondary respectively and Ip and Is are primary and secondary currents.

__Calculation__:

Given that:

N_{p} = 300

N_{s} = 75

I_{s} = 20 A

I_{p} = ?

We know that,

\(\frac{N_{s}}{N_{p}}=\frac{V_{s}}{V_{p}}=\frac{I_{p}}{I_{s}}\)

\(⇒ \frac{N_{s}}{N_{p}}=\frac{I_{p}}{I_{s}}⇒\frac{75}{300}=\frac{I_{p}}{20}\)

⇒ I_{p} = 5 Ampere.

**Hence the current in primary side is 5 Amp.**