The unit of induced emf is

Options

A. ampere
B. volt
C. joule
D. electron volt

Explanation

To find the unit of induced electromotive force (emf), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Induced EMF**:
Induced emf is defined by Faraday's law of electromagnetic induction, which states that the induced emf (E) in a circuit is equal to the negative rate of change of magnetic flux (Φ) through the circuit.

\[ E = -\frac{d\Phi}{dt} \]

2. **Identifying Magnetic Flux**:
Magnetic flux (Φ) is the product of the magnetic field (B) and the area (A) through which the field lines pass, and it is measured in Weber (Wb).

\[ \Phi = B \cdot A \]

3. **Determining the Rate of Change**:
The term \(\frac{d\Phi}{dt}\) represents the rate of change of magnetic flux. The unit of magnetic flux (Weber) can be expressed in terms of its base units:

\[ 1 \, \text{Wb} = 1 \, \text{T} \cdot \text{m}^2 = \frac{\text{kg}}{\text{s}^2} \cdot \text{m}^2 \]

4. **Calculating the Unit of Induced EMF**:
Since induced emf is the rate of change of magnetic flux, we can express its unit as:

\[ \text{Unit of } E = \frac{\text{Unit of } \Phi}{\text{Unit of } t} = \frac{\text{Wb}}{\text{s}} = \frac{\text{T} \cdot \text{m}^2}{\text{s}} = \frac{\text{kg}}{\text{s}^2} \cdot \text{m}^2 \cdot \frac{1}{\text{s}} = \frac{\text{kg} \cdot \text{m}^2}{\text{s}^3} \]

5. **Final Unit of Induced EMF**:
The derived unit of induced emf is equivalent to the unit of voltage, which is the Volt (V).

\[ 1 \, \text{Volt} = 1 \, \frac{\text{Wb}}{\text{s}} = 1 \, \frac{\text{kg} \cdot \text{m}^2}{\text{s}^3} \]

### Conclusion:
Thus, the unit of induced emf is **Volt (V)**.