According to Newton's Third Law, for every action there is an equal an opposite reaction. If the current on the wire is such so that the magnetic force on the wire points upward, what must be true?
According to Newton's Third Law, for every action there is an equal and opposite reaction. In the case of a wire experiencing a magnetic force pointing upward, the wire must be exerting an equal and opposite force on the magnetic field.
To understand why this is true, we can consider how a current-carrying wire interacts with a magnetic field. When an electric current passes through a wire, it creates a magnetic field around it. The direction of this magnetic field is determined by the direction of the current flow.
Now, when a wire carrying current is placed in a magnetic field, a force is exerted on the wire due to the interaction between the magnetic field and the magnetic field created by the current. According to the right-hand rule, the direction of this force is perpendicular to both the direction of the current and the magnetic field.
So, if the magnetic force on the wire is pointing upward, it means that the wire is exerting an equal and opposite force in the opposite direction, which is downward. This is in accordance with Newton's Third Law, as the force exerted by the wire on the magnetic field is equal in magnitude and opposite in direction to the force exerted by the magnetic field on the wire.