The S.I. unit of electric flux is

Options

A. Weber
B. Newton per coulomb
C. Volt `xx` metre
D. Joule per coulomb

Explanation

To determine the S.I. unit of electric flux, we can follow these steps:

### Step 1: Understand the Definition of Electric Flux
Electric flux (\( \Phi \)) is defined as the product of the electric field (\( E \)) and the area (\( A \)) through which the field lines pass. Mathematically, it is expressed as:
\[ \Phi = E \cdot A \]

### Step 2: Identify the Units of Electric Field and Area
- The unit of electric field (\( E \)) is defined as force per unit charge. The unit of force is Newton (N) and the unit of charge is Coulomb (C). Therefore, the unit of electric field is:
\[ [E] = \frac{N}{C} \]
- The unit of area (\( A \)) is square meters (m²):
\[ [A] = m^2 \]

### Step 3: Combine the Units
Now, substituting the units of \( E \) and \( A \) into the formula for electric flux:
\[ [\Phi] = [E] \cdot [A] = \left(\frac{N}{C}\right) \cdot (m^2) = \frac{N \cdot m^2}{C} \]

### Step 4: Relate Newton to Joules
Recall that:
\[ 1 \text{ Joule} (J) = 1 \text{ Newton} (N) \cdot 1 \text{ meter} (m) \]
Thus, we can express Newton in terms of Joules:
\[ N = \frac{J}{m} \]
Substituting this back into the unit of electric flux gives:
\[ [\Phi] = \frac{J}{m} \cdot m^2 \cdot \frac{1}{C} = \frac{J \cdot m}{C} \]

### Step 5: Conclusion
The S.I. unit of electric flux can also be expressed in terms of volts and meters. Since:
\[ 1 \text{ Volt} (V) = \frac{J}{C} \]
We can rewrite the unit of electric flux as:
\[ [\Phi] = V \cdot m \]
Thus, the S.I. unit of electric flux is:
\[ \Phi = \text{Volt} \cdot \text{meter} \quad (V \cdot m) \]

### Final Answer
The S.I. unit of electric flux is **Volt meter (V·m)**.

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