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

Options

A. `3.0V`
B. `0.75 V`
C. `1.5 V`
D. zero

Explanation

To solve the problem regarding the voltage developed in the secondary of a step-up transformer when a Leclanché cell is connected to the primary, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Transformer Basics**:
A transformer works on the principle of electromagnetic induction and is used to change the voltage levels in an AC circuit. A step-up transformer increases the voltage from the primary to the secondary coil.

2. **Identify the Turn Ratio**:
The turn ratio is given as 1:2. This means that for every 1 turn in the primary coil, there are 2 turns in the secondary coil.

3. **Use the Transformer Voltage Formula**:
The relationship between the primary voltage (V_p), secondary voltage (V_s), primary turns (N_p), and secondary turns (N_s) is given by the formula:
\[ \frac{V_s}{V_p} = \frac{N_s}{N_p} \]
In this case, since the turn ratio is 1:2, we can say:
\[ \frac{V_s}{V_p} = \frac{2}{1} \]

4. **Identify the Primary Voltage**:
The primary voltage (V_p) is the EMF of the Leclanché cell, which is given as 1.5 V.

5. **Calculate the Secondary Voltage**:
Using the turn ratio, we can find the secondary voltage (V_s):
\[ V_s = V_p \times \frac{N_s}{N_p} = 1.5 \, \text{V} \times 2 = 3.0 \, \text{V} \]

6. **Consider the Type of Current**:
However, it is important to note that transformers only work with alternating current (AC). The Leclanché cell provides direct current (DC). Therefore, the transformer will not function properly with a DC voltage.

7. **Conclusion**:
Since the transformer cannot operate with a DC source, the voltage developed in the secondary will effectively be zero.

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