CAIE IGCSE Physics 4.5.1.4 Direction of an Induced E M F Opposes Questions
Learn how Lenz law determines induced current direction and how induced currents oppose changes in magnetic flux.
- Syllabus
- 2026–2028
- Course
- Physics 0625
Exam points
- apply Lenz law to explain why induced current opposes the change in magnetic flux
- determine induced current or galvanometer direction from magnet and conductor motion
- explain the opposing magnetic force and field effects caused by induced currents
CAIE IGCSE Physics 4.5.1.4 Direction of an Induced E M F Opposes Questions question 1
Fig. 8.1 shows two vertical, cylindrical tubes and a cylindrical magnet all held in a vacuum.
Fig. 8.1 (not to scale)
One tube is made of plastic and the other tube is made of copper. The two cylindrical tubes have identical dimensions.
The magnetic field of the small, cylindrical magnet is extremely strong.
Initially, the magnet is at rest at the top of the plastic tube.
The magnet is released and it falls through the plastic tube without experiencing a resistive force. The magnet takes 0.67 s to fall to the lower end of the plastic tube.
The magnet is then held at the top of the copper tube and released. As it falls through the copper tube, an electric current is generated in the copper.
The current in the copper produces a magnetic field of its own in the tube. The magnet falls much more slowly in the copper tube than in the plastic tube.
Explain why the magnet falls more slowly in the copper tube.
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