(a) What are magnetic field lines? How is the direction of magnetic field at a point determined? Draw the pattern of magnetic field lines of the magnetic field produced by a current carrying circular loop. Mark on it the direction of (i) current and (ii) magnetic field lines. Name the two factors on which the magnitude of the magnetic field due to a current carrying coil depends. OR (b) Why can't two magnetic field lines cross each other? Draw magnetic field lines showing the direction of the magnetic field due to a current carrying long straight solenoid. State the conclusion which can be drawn from the pattern of magnetic field lines inside the solenoid. Name any two factors on which the magnitude of the magnetic field due to this solenoid depends.

Magnetic field lines are the lines that emerge from the north pole and merge at the south pole of a magnet. The direction of the magnetic field at a point is determined by the direction of the force acting on a small compass needle placed at that point. The pattern of magnetic field lines of the magnetic field produced by a current carrying circular loop is shown below:

The direction of current is shown by the arrows on the loop, and the direction of magnetic field lines is shown by the arrows on the field lines.

The two factors on which the magnitude of the magnetic field due to a current carrying coil depends are:

1. The number of turns of the coil
2. The current flowing through the coil

OR

Two magnetic field lines cannot cross each other because the direction of the magnetic field at a point is unique. If two field lines were to cross each other, it would mean that the direction of the magnetic field at that point is not unique, which is not possible.

The pattern of magnetic field lines due to a current carrying long straight solenoid is shown below:

The conclusion that can be drawn from the pattern of magnetic field lines inside the solenoid is that the magnetic field is uniform inside the solenoid.

The two factors on which the magnitude of the magnetic field due to the solenoid depends are:

1. The number of turns of the solenoid
2. The current flowing through the solenoid