In Activity 13.7, how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased; (ii) a stronger horseshoe magnet is used; and (iii) length of the rod AB is increased?
Answer
We know that
The force by a magnet on a current carrying conductor depends upon

The strength of the magnetic field
Magnetic force exerted by a magnet is directly proportional to the strength of magnetic field.

The amount of current flowing in the conductor
Magnetic force exerted by a magnet is directly proportional to the amount of current flowing in the conductor.

The length of the conductor
Magnetic force exerted by a magnet is directly proportional to the length of the conductor
Now, let's solve the question

current in rod AB is increased
If current in rod AB will increases, the force will also increase.
Since force increases, displacement will also increase.

a stronger horseshoe magnet is used
If a stronger magnet is used, the strength of magnetic field increases.
Since magnetic field increases, force will also increase
Hence,displacement will also increase

length of the rod AB is increased
If length of conductor increases, the force will also increase
Since force increases, displacement will also increase.
Hence, in all 3 cases, displacement will increase