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 problem regarding the behavior of a charge moving across a junction, we can analyze the situation step by step.

### Step 1: Understand the Scenario
A charge is moving through a junction where two different conductive materials meet. This junction can create an electric field due to the accumulation of charges on the surfaces of the wires.

**Hint:** Consider what happens to a charge when it encounters a boundary between two different materials.

### Step 2: Analyze the Forces at the Junction
When the charge approaches the junction, it experiences forces due to the electric field that is generated by the accumulated charges at the junction. This electric field can affect the motion of the charge.

**Hint:** Think about how electric fields influence the motion of charged particles.

### Step 3: Consider Momentum Conservation
Momentum is conserved in a system only when no external forces are acting on it. In this case, the electric field at the junction acts as an external force on the charge, causing a change in its momentum.

**Hint:** Recall the principle of conservation of momentum and when it applies.

### Step 4: Conclusion
Since the charge experiences an external force due to the electric field at the junction, its momentum will not be conserved as it moves across the junction.

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