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In a step up transformer, the turn ratio is $1:2$. A leclanche cell (e.m.f $1.5V$) is connected across the primary. The voltage developed in the secondary would be:
$\begin{align}
  & \text{A}\text{. }0V \\
 & \text{B}\text{. }3.4V \\
 & \text{C}\text{. }4V \\
 & \text{D}\text{. }2V \\
\end{align}$

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Last updated date: 29th Mar 2024
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MVSAT 2024
Answer
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Hint: A transformer is used to increase (step-up) or decrease (step-down) the voltage across an electric circuit. Transformer works on alternating current by the principle of electromagnetic induction. The process of stepping up or stepping down the voltage depends upon the number of turns in primary (input) coil or secondary (output) coil.

Complete step by step answer:
A transformer is defined as a passive electrical device that has the capacity to transfer electrical energy from one circuit to another through the process of electromagnetic induction.
The three main parts of a transformer:
1. Primary Winding of the Transformer
2. Magnetic Core of the Transformer
3. Secondary Winding of the Transformer
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Working Principle of Transformer:
The mutual induction between the two or more windings, also known as coils, allows for electrical energy to be transferred between the electrical circuits.
Let’s say we have a winding which is supplied by an alternating electrical voltage source. The alternating current through the winding will produce a continually varying and alternating magnetic flux that surrounds the winding. If another coil or winding is brought close to this winding, some portion of this alternating magnetic flux will link with the second winding as well. As this magnetic flux is continually varying in its amplitude and direction, there must be a changing flux linkage in the second winding or coil. According to Faraday’s law of electromagnetic induction, there will be an EMF induced in the second winding. If the circuit of this secondary winding is closed, then electric current will flow through it.
Transformers are used to increase, step up, or decrease, step down, voltage levels between the electric circuits. A transformer that increases the voltage between primary winding to secondary winding is defined as a step-up transformer, whereas, a transformer that decreases the voltage between primary winding to secondary winding is defined as a step-down transformer.
The process of stepping up and stepping down the voltage depends upon the number of turns in the primary and secondary coil. For stepping up the voltage, the number of turns in secondary should be more than the number of turns in primary coil, while for stepping down the voltage, the number of turns in secondary should be less than the number of turns in primary coil.
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Leclanche cell works on Direct Current (DC) and therefore gives direct current as its output. The turn ratio has no significance here because the transformer works on Alternating current (AC) and not on Direct Current (DC). As the input from a leclanche cell does not vary with time, the magnetic flux linked with the secondary also remains constant and thus the induced emf across secondary is zero. The output will be zero.
The voltage developed across the secondary would be $0V$.

Hence, the correct option is A.

Note:
Transformers work on Alternating current since its value continuously keeps on changing with time. The reason behind the induced emf in the secondary coil is the changing amount of current which results in continuously varying magnetic flux across the secondary coil. The purpose of the transformer core is to provide a low reluctance (less opposition) path, through which the maximum amount of flux produced by the primary winding is passed through and linked with the secondary winding to provide the maximum output.
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