Question

One of Maxwell's Equations can be written as $\oint \overrightarrow{B}.d\overrightarrow{A}=0$.
Which of the following statements follows directly from this statement? Select two answers.

• A. Magnetic field lines must form closed loops.
• B. Moving charges create magnetic field.
• C. There exist no magnetic monopoles.
• D. Magnetic field is directed away from the north pole of a bar magnet and toward the south pole.
• E. Magnetic field strength decreases with increasing distance from the source.

Answer 1

The correct option is A Magnetic field lines must form closed loops.

Maxwell's equation $\oint \overrightarrow{B}.\overrightarrow{A}=0$ , says that the number of field lines going in any volume , equals the number of lines coming out from the same volume , it means magnetic field lines must be closed loops or we can say that they cannot start from anywhere i.e. there exist no magnetic monopoles .