E.m.f. of a cell is measured in

Options

A. J
B. `JC ^(-1)`
C. `Nkg^(-1)`
D. `W m ^(-2)`

Answer

To determine the unit of electromotive force (E.M.F.) of a cell, we can follow these steps:

### Step 1: Understand the Definition of E.M.F.
E.M.F. stands for electromotive force, which is defined as the energy provided by a cell or battery per unit charge.

### Step 2: Write the Formula for E.M.F.
The formula for E.M.F. can be expressed as:
\[ \text{E.M.F.} = \frac{E}{Q} \]
Where:
- \( E \) is the energy supplied by the cell (in joules),
- \( Q \) is the charge (in coulombs).

### Step 3: Analyze the Units
From the formula, we can deduce the units of E.M.F.:
- The unit of energy \( E \) is joules (J).
- The unit of charge \( Q \) is coulombs (C).

Thus, the unit of E.M.F. can be expressed as:
\[ \text{Unit of E.M.F.} = \frac{\text{Joules}}{\text{Coulombs}} = \text{Joule per Coulomb} \]

### Step 4: Identify the Correct Option
The unit of E.M.F. (Joule per Coulomb) is also known as a volt (V). Therefore, we can say:
\[ 1 \text{ Volt} = 1 \frac{\text{Joule}}{\text{Coulomb}} \]

Looking at the options provided:
1. Joule
2. Joule per Coulomb
3. Newton per Kilogram
4. Watt per Meter squared

The correct answer is **option 2: Joule per Coulomb**.

### Final Answer
The E.M.F. of a cell is measured in **Joule per Coulomb**.

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