Q127 / 150 · MHT CET 2026 (15 April Shift 1) · Physics
A bar magnet falls from a height 'h' through a metal pipe, its acceleration after coming out of pipe is
- Aless than $9.8 \text{ m/s}^2$
- Bgreater than $9.8 \text{ m/s}^2$
- Correct answerCequal to $9.8 \text{ m/s}^2$
- Dequal to 'h' $\text{m/s}^2$
Solution
When the bar magnet falls through the metal pipe, the changing magnetic flux induces eddy currents in the pipe.
According to Lenz's law, these eddy currents oppose the motion of the magnet, making its acceleration less than $g$ ($9.8 \text{ m/s}^2$) while inside the pipe.
Once the magnet comes out of the pipe, there is no induced current to oppose its motion.
The only force acting on the magnet is gravity.
Therefore, its acceleration after coming out of the pipe is equal to the acceleration due to gravity, which is $9.8 \text{ m/s}^2$.
According to Lenz's law, these eddy currents oppose the motion of the magnet, making its acceleration less than $g$ ($9.8 \text{ m/s}^2$) while inside the pipe.
Once the magnet comes out of the pipe, there is no induced current to oppose its motion.
The only force acting on the magnet is gravity.
Therefore, its acceleration after coming out of the pipe is equal to the acceleration due to gravity, which is $9.8 \text{ m/s}^2$.
Hence, the correct answer is option: 'C'.