iGCSE Physics (0625) 4.5.1 Electromagnetic induction -Exam Style Questions Paper 2 - New Syllabus
▶️ Answer/Explanation
Detailed solution:
This question is governed by Lenz’s Law, which states that the direction of an induced current is such that it creates a magnetic effect to oppose the change that produced it. The “change” in this scenario is the downward motion of the wire through the magnetic field. To oppose this downward movement, the induced current must generate a magnetic force acting in the opposite direction. Since the wire is being moved toward the bottom of the page, the opposing force must act toward the top of the page. This ensures the principle of conservation of energy is upheld by requiring work to be done against this resistive force.
▶️ Answer/Explanation
Detailed solution:
To determine the direction of motion, we apply Fleming’s Right-Hand Rule for induced current.
The First Finger represents the magnetic field, pointing from North ($N$) to South ($S$) (rightward).
The Second Finger represents the direction of the induced current, which is pointing “out of the page” toward the observer as shown by the arrow on the wire.
The Thumb then points in the direction of the Motion (force) applied to the wire.
Aligning your hand accordingly, the thumb points vertically downward toward C.
Thus, to induce a current in the direction indicated, the wire must be moved in direction C.
▶️ Answer/Explanation
Detailed solution:
A generator works on the principle of electromagnetic induction, where a changing magnetic field induces an electromotive force ($e.m.f.$) in a conductor.
According to Faraday’s Law, the magnitude of the induced $e.m.f.$ is directly proportional to the rate of change of magnetic flux linkage.
Increasing the number of turns ($N$) on the stationary coil increases the total flux linkage, thereby resulting in a higher output $e.m.f$.
Options A and B are incorrect because increasing rotation speed or magnet strength actually increases the induced current.
Option C is incorrect because a larger gap weakens the magnetic field strength at the coil, which reduces the induced $e.m.f$.
Therefore, statement D is the only correct physical description of how to increase the generator’s output.