JEE Main
- Exam
- JEE Main
- Subject
- Physics
- Chapter
- Magnetic Properties of Matter
JEE Main · Physics · Magnetic Properties of Matter
Two pendulums, one with a solid copper plate as its bob and the...
Two pendulums, one with a solid copper plate as its bob and the other with a slotted copper plate of identical outer dimensions, are made to swing from the same initial angle between the pole pieces of a strong electromagnet. Which of the following statements correctly describes their motion?
Options
- AThe slotted plate comes to rest faster because the slots increase air resistance during the swing.
- BBoth plates come to rest at the same time because copper is a non-magnetic material and unaffected by the magnetic field.
- CThe slotted plate comes to rest faster because the magnetic flux can penetrate deeper into the gaps, creating a stronger retarding force.
- DThe solid plate comes to rest faster because continuous conducting paths allow larger eddy currents to be induced, providing a greater opposing force.
Correct answer
D. The solid plate comes to rest faster because continuous conducting paths allow larger eddy currents to be induced, providing a greater opposing force.
Step-by-step solution
As the solid copper plate swings through the magnetic field, the changing magnetic flux induces large eddy currents in the bulk of the copper.
According to Lenz's law, these eddy currents interact with the magnetic field to produce a strong electromagnetic damping force that opposes the motion, causing the solid plate to come to rest quickly.
In the slotted plate, the slots break the continuous conducting paths, which significantly restricts the formation of large eddy current loops. As a result, the electromagnetic damping is much weaker, and the slotted plate swings for a longer time.
Therefore, the solid plate experiences greater damping and comes to rest faster.
Answer: The solid plate comes to rest faster because continuous conducting paths allow larger eddy currents to be induced, providing a greater opposing force.
According to Lenz's law, these eddy currents interact with the magnetic field to produce a strong electromagnetic damping force that opposes the motion, causing the solid plate to come to rest quickly.
In the slotted plate, the slots break the continuous conducting paths, which significantly restricts the formation of large eddy current loops. As a result, the electromagnetic damping is much weaker, and the slotted plate swings for a longer time.
Therefore, the solid plate experiences greater damping and comes to rest faster.
Answer: The solid plate comes to rest faster because continuous conducting paths allow larger eddy currents to be induced, providing a greater opposing force.