A charge is moving across a junction, then

Options

A. momentum will be conserved
B. momentum will not be conserved
C. at some places momentum be conserved and at other places momentum will not be conserved
D. none of these.

Answer

To solve the question regarding the conservation of momentum for a charge moving across a junction, let's break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Scenario**: We have a charge moving through a wire and approaching a junction. At this junction, the behavior of the charge and the surrounding charges needs to be analyzed.

2. **Charge Movement**: As the charge moves towards the junction, it interacts with the charges present in the wire. This interaction is crucial for understanding momentum conservation.

3. **Charge Accumulation**: When the charge approaches the junction, it causes a redistribution of charges in the wire. Electrons may accumulate at the junction due to the influence of the moving charge.

4. **Electric Field Generation**: The accumulation of charges at the junction creates an electric field. This electric field can exert a force on the moving charge, altering its momentum.

5. **Momentum Change**: Since the electric field generated by the accumulated charges can change the direction of the moving charge, the momentum of the charge is affected. The momentum of a charge is defined as the product of its mass and velocity, and any change in velocity (due to the electric field) means a change in momentum.

6. **Conclusion on Momentum Conservation**: Because the moving charge experiences a force due to the electric field created by the accumulated charges, the momentum of the charge is not conserved at the junction.

7. **Final Answer**: Therefore, the correct option is that the momentum will not be conserved when a charge moves across a junction.