Assertion: Power of a magetic force on a charged particle is always zero.
Reason: Power of electric force on charged particle cannnot be zero.

Options

A. If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
C. If Assertion is true, but the Reason is false.
D. If Assertion is false but the Reason is true.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided, and determine their validity.

### Step 1: Analyze the Assertion
The assertion states that "Power of a magnetic force on a charged particle is always zero."

- The magnetic force \( \mathbf{F} \) on a charged particle moving with velocity \( \mathbf{V} \) in a magnetic field \( \mathbf{B} \) is given by:
\[ \mathbf{F} = Q (\mathbf{V} \times \mathbf{B}) \]
where \( Q \) is the charge of the particle.

- The power \( P \) delivered by a force is given by the dot product of the force and the velocity:
\[ P = \mathbf{F} \cdot \mathbf{V} \]

- Since the magnetic force is always perpendicular to the velocity of the charged particle (as it is a cross product), the dot product \( \mathbf{F} \cdot \mathbf{V} \) will always be zero:
\[ P = \mathbf{F} \cdot \mathbf{V} = 0 \]

Thus, the assertion is **true**.

### Step 2: Analyze the Reason
The reason states that "Power of electric force on charged particle cannot be zero."

- The electric force \( \mathbf{F_E} \) on a charged particle is given by:
\[ \mathbf{F_E} = Q \mathbf{E} \]
where \( \mathbf{E} \) is the electric field.

- The power delivered by the electric force is:
\[ P_E = \mathbf{F_E} \cdot \mathbf{V} \]

- The power can be zero if the electric force is perpendicular to the velocity of the charged particle. Therefore, it is not necessarily true that the power of the electric force cannot be zero; it can be zero in certain configurations.

Thus, the reason is **false**.

### Conclusion
- The assertion is true, and the reason is false. Therefore, the correct answer is that the assertion is true, but the reason is not a correct explanation for the assertion.

### Final Answer
The assertion is true, and the reason is false.

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