A stream of electrons is projected horizontally to the right. A straight conductor carrying a current is supported parallel to the electron steam an above it. If the current in the conductor is from left to right, what will be the effect on the electron stream?

Options

A. The electron stream will be pulled upward
B. The correct stream will be pulled downward
C. The electron stream will be retarded
D. The electron stream will be speeded up toward the right

Explanation

### Step-by-Step Solution:

1. **Identify the Direction of the Electron Stream**:
- The electron stream is projected horizontally to the right. Since electrons are negatively charged, the conventional current (I) due to this stream flows in the opposite direction, which is to the left.

2. **Identify the Direction of the Current in the Conductor**:
- The straight conductor carries a current from left to right. This means the current in the conductor is flowing in the same direction as the conventional current of the electron stream.

3. **Determine the Relationship Between the Currents**:
- Since the current in the conductor (I) is flowing from left to right and the current due to the electron stream (i) is flowing from right to left, the two currents are anti-parallel.

4. **Apply the Right-Hand Rule**:
- To determine the magnetic field direction created by the current in the conductor, use the right-hand rule: point your thumb in the direction of the current (left to right), and your fingers will curl in the direction of the magnetic field lines, which will circle around the conductor.

5. **Determine the Effect of the Magnetic Field on the Electron Stream**:
- The magnetic field produced by the current in the conductor will exert a force on the moving electrons. According to the Lorentz force law, the force on a charge moving in a magnetic field is given by \( \vec{F} = q(\vec{v} \times \vec{B}) \).
- In this case, the velocity of the electrons (\( \vec{v} \)) is to the right, and the magnetic field (\( \vec{B} \)) due to the current in the conductor is directed downward (using the right-hand rule).

6. **Determine the Direction of the Force on the Electrons**:
- Using the right-hand rule for the cross product, with your fingers pointing in the direction of the electron's velocity (to the right) and curling in the direction of the magnetic field (downward), your palm will face towards you, indicating that the force on the electrons will be directed downward.

7. **Conclusion**:
- Therefore, the effect on the electron stream is that it will be pulled downward due to the repulsive force generated by the interaction of the magnetic field and the moving electrons.

### Final Answer:
The electron stream will be pulled downward.

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