Question

Which of the following is not correct about magnetic field lines?
A) Magnetic field lines of a magnet form continuous closed loops.
B) The tangent to the field line at a given point represents the direction of net magnetic field B at that point.
C) The larger the number of field lines crossing per unit area, the stronger is the magnitude of the magnetic field B.
D) The magnetic field lines may intersect to each other in certain conditions.

Answer 1

Hint: Magnetic field lines come from a magnet. These lines come out of one pole of magnet and go into the other pole. These lines are of circular shape. Magnetic field arises because of these lines.

Complete answer:
Magnetic field lines arise from a magnet. These lines have some specific properties; these properties give magnetic field lines of too much importance. Following are some properties of magnetic field lines:
1. The magnetic field magnitude is proportional to the density of magnetic field lines. It is proportional to the number of magnetic field lines per unit area.
2. Magnetic field lines do not intersect each other.
3. Magnetic field lines come out of the North Pole and it goes into the South Pole.
4. Magnetic field lines form circular closed loops.
The direction of the magnetic field is tangent to the field line at every point in space.
From the above explanation, we can see that option (D) contradicts the properties of magnetic field lines.

Hence, option (D) is correct.

Note: Magnetic field lines play a very important role in a system having magnetic fields. Fourth property of magnetic field lines shows that the North Pole and South Pole can never be separated. It means that monopoles cannot exist. Many of the properties of magnetic field lines are similar to that of electric field lines. But the property that magnetic field lines form closed loops is different from that of electric field lines. Because the electric field line comes out of a positive charge and it goes into negative charge. But electric field lines do not form closed loops.