Identify the false statement

Options

A. Electric field is zero inside the conductor and just outside, it is normal to the surface
B. Electric field is zero in the cavity of a hollow charged conductor
C. A polar dielectric is one which is having a net dipole moment zero in the absence of electric field
D. `H_(2),N_(2),O_(2),CO_(2) and CH_(4)` are examples of polar dielectric

Answer

To solve the question of identifying the false statement among the given options, we will analyze each statement step by step.

### Step 1: Analyze the First Statement
**Statement:** Electric field is zero inside the conductor and just outside it is normal to the surface.

**Explanation:**
- Inside a conductor in electrostatic equilibrium, the electric field is indeed zero. This is because charges redistribute themselves on the surface of the conductor, leading to no net charge within the conductor.
- Just outside the surface of the conductor, the electric field lines are normal (perpendicular) to the surface. This is due to the fact that electric field lines originate from positive charges and terminate on negative charges, and they do so at right angles to the surface of the conductor.

**Conclusion:** This statement is true.

### Step 2: Analyze the Second Statement
**Statement:** Electric field is 0 in the cavity of a hollow charged conductor.

**Explanation:**
- For a hollow charged conductor, the electric field inside the cavity is also zero. This is a direct consequence of Gauss's law, which states that the electric field inside a closed conductor is zero when in electrostatic equilibrium.

**Conclusion:** This statement is true.

### Step 3: Analyze the Third Statement
**Statement:** A polar dielectric is one in which the net dipole moment is zero in the absence of an electric field.

**Explanation:**
- A polar dielectric is characterized by having permanent dipoles. However, in the absence of an external electric field, the orientation of these dipoles may lead to a net dipole moment of zero due to random orientations.
- Therefore, this statement is misleading. A polar dielectric has a dipole moment, but the net dipole moment can be zero if the dipoles are randomly oriented.

**Conclusion:** This statement is misleading and can be considered false.

### Step 4: Analyze the Fourth Statement
**Statement:** CO2 and CH4 are polar dielectrics.

**Explanation:**
- CO2 (carbon dioxide) and CH4 (methane) are actually non-polar molecules because of their symmetrical geometry, which leads to a cancellation of dipole moments.
- Therefore, stating that CO2 and CH4 are polar dielectrics is incorrect.

**Conclusion:** This statement is false.

### Final Conclusion
After analyzing all the statements, we find that the third statement about polar dielectrics is misleading, and the fourth statement about CO2 and CH4 being polar dielectrics is definitively false.

### Summary of False Statement
The false statement is: **"A polar dielectric is one in which the net dipole moment is zero in the absence of an electric field."**