in a step-up transformer, the turn ratio is `1:2` leclanche cell (e.m.f. 1.5V) is connected across the primary. The voltage devloped in the secondary would be

Options

A. 3 V
B. `1.5 V`
C. `0.75 V`
D. zero

Explanation

To solve the problem, we need to understand the operation of a step-up transformer and the implications of connecting a Leclanché cell (which provides direct current) to its primary coil. Here’s a step-by-step solution:

### Step 1: Understand the Turn Ratio
The turn ratio of a transformer is defined as the ratio of the number of turns in the secondary coil (Ns) to the number of turns in the primary coil (Np). In this case, the turn ratio is given as 1:2.

### Step 2: Determine the Primary Voltage
The voltage across the primary (Vp) is given as the e.m.f. of the Leclanché cell, which is 1.5 V.

### Step 3: Apply the Transformer Equation
For a transformer, the relationship between the primary voltage (Vp), secondary voltage (Vs), and the turn ratio (Ns/Np) is given by the formula:
\[ \frac{Vs}{Vp} = \frac{Ns}{Np} \]

### Step 4: Substitute Known Values
From the turn ratio of 1:2, we can express it as:
\[ \frac{Ns}{Np} = \frac{2}{1} \]
Now substituting the known values into the transformer equation:
\[ \frac{Vs}{1.5} = \frac{2}{1} \]

### Step 5: Solve for Secondary Voltage (Vs)
Rearranging the equation to find Vs:
\[ Vs = 1.5 \times 2 = 3 \, \text{V} \]

### Step 6: Consider the Nature of Current
However, it is important to note that a transformer operates on alternating current (AC) and not direct current (DC). The Leclanché cell provides DC, which means that no alternating magnetic field is produced in the primary coil.

### Step 7: Conclusion
Since a transformer requires an alternating current to function, and we are connecting a DC source, there will be no change in magnetic flux, and thus no voltage will be induced in the secondary coil. Therefore, the voltage developed in the secondary (Vs) will be:
\[ Vs = 0 \, \text{V} \]

### Final Answer
The voltage developed in the secondary would be **0 V**.

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