Electricity may be generated by rotating a loop of wire between the poles of a magnet. The induced current is greatest when a. the plane of the loop is parallel to the magnetic field. b. the plane of the loop is perpendicular to the magnetic field. c. the magnetic flux through the loop is a minimum. d. the plane of the loop makes an angle of 45° with the magnetic field.
The correct answer is option b. The induced current is greatest when the plane of the loop is perpendicular to the magnetic field.
To understand why, we need to know about Faraday's Law of Electromagnetic Induction. According to this law, an electromotive force (EMF) is induced in a wire when it cuts through magnetic field lines. The magnitude of this induced EMF is directly proportional to the rate at which the magnetic field lines are cut.
When the loop of wire is parallel to the magnetic field (option a), the wire is not cutting through many magnetic field lines, resulting in a smaller induced EMF. Similarly, when the plane of the loop makes an angle of 45° with the magnetic field (option d), the wire is cutting through fewer magnetic field lines compared to when it is perpendicular to the field, resulting in a reduced induced EMF.
On the other hand, when the plane of the loop is perpendicular to the magnetic field (option b), the wire cuts through the maximum number of magnetic field lines per unit time. This results in the maximum rate of change of magnetic flux and thus the greatest induced EMF and current.
So, option b is the correct choice because it maximizes the induction of current in the wire.