A charge `+ Q` is moving upwards vertically. It enters a magnetic field directed to the north. The force on the charge will be towards

Options

A. North
B. South
C. East
D. West

Answer

To determine the direction of the force on a charge \( +Q \) moving in a magnetic field, we can use the right-hand rule. Here’s a step-by-step solution:

### Step 1: Identify the Directions
- The charge \( +Q \) is moving vertically upwards. We can denote this direction as the positive \( z \)-axis.
- The magnetic field is directed to the north. We can denote this direction as the positive \( y \)-axis.

### Step 2: Apply the Right-Hand Rule
- According to the right-hand rule for the cross product \( \vec{F} = Q (\vec{V} \times \vec{B}) \):
- Point your fingers in the direction of the velocity vector \( \vec{V} \) (upwards).
- Curl your fingers in the direction of the magnetic field vector \( \vec{B} \) (to the north).
- Your thumb will then point in the direction of the force \( \vec{F} \) acting on the charge.

### Step 3: Determine the Force Direction
- With your fingers pointing upwards (in the direction of \( +Q \)) and curling towards the north (in the direction of the magnetic field), your thumb will point towards the east.
- Therefore, the force on the charge \( +Q \) will be directed towards the east.

### Final Answer
The force on the charge \( +Q \) will be towards the east.

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