Test Physics Num 2

Explanation
When a compass is placed next to a bar magnet, the pointer on the compass, which is the north pole of a small magnet, will align itself with the magnetic field lines of the bar magnet. The magnetic field lines of a bar magnet extend from the north pole to the south pole. Since opposite poles attract, the north pole of the compass magnet will point towards the south pole of the bar magnet. Therefore, the pointer on the compass will point in the direction opposite to the north pole of the bar magnet, which is to the right.

Explanation
When the current in a wire is doubled, the magnetic force acting on the wire is quartered. This is because the magnetic force is directly proportional to the current in the wire. When the current is doubled, the force becomes four times smaller (quartered) to maintain the equilibrium.

Explanation
When a positively charged particle moves in a circular path in a clockwise direction, it experiences a magnetic force directed towards the center of the circle. According to the right-hand rule, the direction of the magnetic field lines is perpendicular to the plane of the page and points out of the page. This is because the magnetic field lines must be oriented in a way that generates a force towards the center of the circle, which corresponds to the particle's motion.

Explanation
To maximize the magnitude of the magnetic force acting on a charged particle moving in a magnetic field, one should maximize the strength of the magnetic field. This is because the magnetic force is directly proportional to the strength of the magnetic field. Minimizing the particle's velocity or ensuring that the particle is moving in the same direction as the magnetic field lines does not have an effect on the magnitude of the magnetic force.

Explanation
When the strength of the magnetic field doubles, the radius of the charged particle's orbit gets halved. This is because the centripetal force required to keep the particle in circular motion is provided by the magnetic force acting on the particle. The magnetic force is given by the equation F = qvB, where q is the charge of the particle, v is its velocity, and B is the magnetic field strength. As the magnetic field strength doubles, the force experienced by the particle also doubles. To maintain equilibrium, the radius of the orbit must decrease to compensate for the increased force, resulting in a halving of the radius.

Explanation
When two wires carry current in opposite directions, they create magnetic fields that interact with each other. According to the right-hand rule, the magnetic field lines around each wire will form loops, and these loops will intersect and interact with each other. The interaction between the magnetic fields created by the currents in the wires results in a repulsive force between the wires. This repulsive force is represented by the graph "Two-wire carry current in opposite directions repel each other."

Explanation
The magnetic field is strongest at point b because it is closest to the wire. According to the right-hand rule, the magnetic field lines around a current-carrying wire form concentric circles centered on the wire. The strength of the magnetic field decreases as you move further away from the wire. Therefore, point b, being the closest point to the wire, experiences the strongest magnetic field.