The motioin of a charged particle can be used ot distinguish between a magnetic field and electric field in a certain region by firing the charge

Options

A. Perpendicular to the field
B. From opposite directions
C. From opposite directions
D. With different speeds

Answer

To distinguish between a magnetic field and an electric field using the motion of a charged particle, we can analyze the forces acting on the particle when it is fired in different directions relative to the fields. Here’s a step-by-step solution to the question:

### Step 1: Understanding the Forces
When a charged particle moves in an electric field, it experiences an electric force given by:
\[ \vec{F}_E = q \vec{E} \]
where \( q \) is the charge of the particle and \( \vec{E} \) is the electric field.

In a magnetic field, the force acting on the charged particle is given by:
\[ \vec{F}_B = q (\vec{v} \times \vec{B}) \]
where \( \vec{v} \) is the velocity of the particle and \( \vec{B} \) is the magnetic field.

### Step 2: Analyzing Motion Parallel to the Field
If the charged particle is fired parallel to the electric field, it will experience an electric force acting in the same direction as its motion. The particle will accelerate due to this force.

However, if the particle is fired parallel to the magnetic field, the magnetic force will not act on it because the magnetic force depends on the cross product of the velocity and the magnetic field. Thus, the magnetic force will be zero when the velocity is parallel to the magnetic field.

### Step 3: Conclusion on Distinguishing Fields
To distinguish between the electric field and the magnetic field:
- If the charged particle is fired **parallel to the field** (either electric or magnetic), it will only experience the electric force and will accelerate.
- If it is fired **perpendicular to the field**, it will experience forces from both fields, and the motion will be more complex.

Thus, the correct way to distinguish between the two fields is to fire the charged particle **parallel to the electric field**. The electric field will cause acceleration, while the magnetic field will not have any effect.

### Final Answer
The correct option is: **firing the charge parallel to the field**.

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