An electron falling freely under gravity entersa region of uniform horizontal magnetic field pointing north to south. The particle will be deflected towards

Options

A. east
B. west
C. north
D. south

Answer

To solve the problem, we need to analyze the motion of an electron in a magnetic field. The steps are as follows:

### Step 1: Identify the Directions
- The electron is falling freely under gravity, which means its velocity is directed downward (towards the ground).
- The magnetic field is uniform and directed from north to south.

### Step 2: Determine the Charge of the Particle
- The particle in question is an electron, which has a negative charge (Q = -e).

### Step 3: Use the Right-Hand Rule
- The magnetic force acting on a charged particle moving in a magnetic field is given by the equation:
\[ \vec{F} = Q (\vec{V} \times \vec{B}) \]
where:
- \( \vec{F} \) is the magnetic force,
- \( Q \) is the charge of the particle,
- \( \vec{V} \) is the velocity of the particle,
- \( \vec{B} \) is the magnetic field.

### Step 4: Apply the Right-Hand Rule
- For a positive charge, you would use your right hand:
- Point your fingers in the direction of the velocity (downward).
- Curl them in the direction of the magnetic field (from north to south).
- Your thumb will point in the direction of the force.

- Since the electron is negatively charged, the force will be in the opposite direction of what the right-hand rule indicates.

### Step 5: Determine the Resulting Direction
- If we apply the right-hand rule for the velocity (downward) and the magnetic field (north to south), the thumb points towards the west for a positive charge.
- However, since the electron is negatively charged, the magnetic force will be directed opposite to this, which means the force will be directed towards the east.

### Conclusion
Thus, the electron will be deflected towards the east.