Question

A magnet is placed in earth’s magnetic field with the North Pole of the magnet pointing north. At the neutral point
This question has multiple correct options
A. The earth’s magnetic field is zero
B. The magnet’s magnetic field is zero
C. The net magnetic field is $0$
D. The magnetic fields of the magnet and the earth are equal and opposite.

Answer 1

At first recall what a neutral point is, what are the conditions required for a neutral point. The question has multiple options correct so check each option carefully one by one. Compare the conditions required for a neutral point with the options given and select the correct options.

Complete answer:
First let us understand what a neutral point is. Suppose two magnetic fields are present and at a point the resultant of two magnetic fields is zero or net magnetic field is zero then it is known as a neutral point. As the question has multiple correct options, let’s check the options one by one.

Option A The earth’s magnetic field is zero: This option is incorrect as, earth’s magnetic field intensity is between $0.25\,{\text{Gauss}}$ and $0.65\,{\text{Gauss}}$ so, the earth’s magnetic field is not zero.

Option B The magnet’s magnetic field is zero: This option is incorrect as there will be a magnetic field of a magnet, if its magnetic field is zero then it cannot act as a magnet.

Option C The net magnetic field is $0$: This option is correct. As for neutral points the resultant magnetic field or net magnetic field should be zero.

Option D The magnetic fields of the magnet and the earth are equal and opposite: This option is correct because at some point the magnetic field of the magnet and earth’s magnetic field may be equal and be in opposite directions so at that point net magnetic field will be zero and it will be a neutral point.

Hence, the correct options are C and D.

Note: The geographical North Pole of earth is actually the South Pole of earth’s magnetic field and geographical South Pole of earth is actually North Pole of earth’s magnetic field. In the case of magnets, unlike attracts, the South Pole attracts North and vice versa. So, when a compass points towards the North Pole it is attracted to the actual South point of the earth.