Suppose that now the magnetic field is reversed, i. e., it is coming out of the page. The charges q1 and q2 are positive, and the charges

q3 and q4 are negative. How many of the display paths are incorrect?

To determine the number of incorrect display paths, we first need to understand the concept of display paths and how they are affected by a reversed magnetic field.

A display path refers to the path that charged particles take when moving in a magnetic field. The direction of the magnetic field determines the direction of the force on the charges, which in turn determines the path they follow.

In this case, the magnetic field is coming out of the page, which means it is directed towards us. Let's analyze each charge and determine their respective display paths:

1. Charge q1 (positive): Since q1 is positive, it experiences a force in a direction perpendicular to both the magnetic field and its velocity. Since the velocity of q1 is not specified, the display path can be either clockwise or counterclockwise around the magnetic field lines.

2. Charge q2 (positive): Similar to q1, q2 is positive and will experience a force perpendicular to its velocity and the magnetic field direction. The display path can also be clockwise or counterclockwise.

3. Charge q3 (negative): Negative charges experience a force in the opposite direction compared to positive charges. Therefore, q3 will move in a direction opposite to q1 and q2. Since the magnetic field is directed towards us, q3 will move clockwise around the magnetic field lines.

4. Charge q4 (negative): Similar to q3, q4 is negative and will move in the same direction as q3, which is clockwise around the magnetic field lines.

Now, let's consider the statement of "incorrect display paths." This refers to paths that are not consistent with the behavior of the charges in a reversed magnetic field.

Based on our analysis, the only charges whose display paths can be incorrect are q1 and q2 since their paths can be either clockwise or counterclockwise due to their positive charge. The display paths of q3 and q4 are determined by their negative charge, making them always move in a clockwise direction.

Therefore, the number of incorrect display paths is determined by the number of possible display paths for q1 and q2. As there are two options (clockwise and counterclockwise), there are two possible incorrect display paths.