A: The trajectory of a charge when it is projected perpendicular to an electric fiedl is a parabola.
R: A moving charge entering parallel to the magnetic field lines moves in a circular path.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark 2.
C. If assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the assertion and reason question, we will analyze both statements step by step.

### Step 1: Analyze the Assertion
The assertion states: "The trajectory of a charge when it is projected perpendicular to an electric field is a parabola."

- When a charged particle (like an electron or proton) is projected into an electric field, it experiences a force due to the electric field. This force is given by \( F = qE \), where \( q \) is the charge and \( E \) is the electric field strength.
- If the charge is projected perpendicular to the electric field, it will have an initial velocity component that is perpendicular to the direction of the electric field.
- The electric force will act in the direction of the electric field, causing the particle to accelerate in that direction while it continues to move forward. This results in a parabolic trajectory, similar to the motion of a projectile under gravity.

**Conclusion for Assertion**: The assertion is **true**.

### Step 2: Analyze the Reason
The reason states: "A moving charge entering parallel to the magnetic field lines moves in a circular path."

- When a charged particle moves in a magnetic field, it experiences a magnetic force given by \( F = q(v \times B) \), where \( v \) is the velocity of the charge and \( B \) is the magnetic field.
- If the charge enters the magnetic field parallel to the field lines (i.e., in the same direction as the magnetic field), the angle between the velocity vector and the magnetic field vector is zero. In this case, the magnetic force becomes zero because the cross product \( v \times B \) equals zero.
- Therefore, the charge will not experience any magnetic force and will continue to move in a straight line, not in a circular path.

**Conclusion for Reason**: The reason is **false**.

### Final Conclusion
- The assertion is true, and the reason is false. Therefore, the correct answer is option C: Assertion is true, and Reason is false.

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