Question

Briefly explain an activity to plot the magnetic field lines around a straight current carrying conductor. Sketch the field pattern for the same, specifying current and field directions. What happens to the field? (a) if the strength of the current is decreased. (b) if the direction of the current is reversed.

Answer 1

If the current will be increased then magnetic field will increase and will reverse its direction if the direction of the current is reversed.

• B = μ₀I/2πr ,as B is directly proportional to the current so it will increase if the current is increased
• The direction of current is given by the right hand thumb rule so if the direction of the current is reversed then the direction of magnetic field will be also reversed.
• In order to perform an activity to plot magnetic field take iron fills and place them on a piece of paper or cardboard and then pass a straight wire through the middle of the paper, you will be able to see that iron fill align in the direction of magnetic field.
• Or you can also use a magnetic compass to see the direction of the magnetic field.

Answer 2

The compass needle shows that the magnetic lines are in clockwise direction.

Explanation:

• Take  cardboard in which Current flows from X to Y direction.
• When iron fillings are sprinkled on the cardboard they arrange themselves in concentric circles around the wire which represent magnetic field lines.
• Compass needle is used to determine the direction of lines. The compass needle shows that the line are in clockwise direction.
• (a) The magnetic filed also decrease when the current is decreased.
• (b) The magnetic filed is reversed when the direction of current is reversed.