Question

A strong horseshoe magnet is closed by an iron plate $\text{A}$. The weight of the plate corresponds to the lifting force of the magnet, and the magnet can easily hold the plate. If the poles of the magnet are now touched on the sides with a plate $\text{B}$ made of the soft iron, then plate $\text{A}$ falls instantly. If the plate $\text{B}$ is removed the magnet will again be capable of holding the plate $\text{A}$. This happened because

• A. Magnetic lines of force are short-circuited through plate $\text{B}$
• B. the force of interaction between the magnet and plate $\text{A}$ decreases.
• C. the force of interaction between the magnet and plate $\text{A}$ increases.
• D. Number of the lines of force passes through plate $\text{A}$ sharply decreases.

Answer 1

Answer: (A), (B), (D)

Number of the lines of force passes through plate $\text{A}$ sharply decreases.


When plate $\text{B}$ brought in contact with the bar magnet, A part of the magnetic lines of force are short-circuited through this plate. The Number of the lines of force penetrating through plate $\text{A}$ sharply decreases. As a result magnetic force interaction between the magnet and plate $\text{A}$ also decreases consequently it falls down.

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, options $\left(A\right),\left(B\right)$ and $\left(D\right)$ are the correct answer.