Question

Magnetic dipole moment of a rectangular loop is _.
A. Inversely proportional to current in loop
B. Inversely proportional to area of loop
C. Parallel to plane of loop and proportional to area of loop
D. Perpendicular to plane of loop and proportional to area of loop

Answer 1

Hint:To answer this question, you need to know what magnetic moment is and what all are the factors affecting magnetic moment. Recall what magnetic moment indicates and how it is measured. This question is based on the basics of magnetism and measures your knowledge in magnetism.





Formula Used:
We have an equation for magnetic dipole moment of a loop as:
$\mu =IA$
Where I is the current carried by the loop and A is the area of the loop.




Complete answer:
Magnetic dipole moment is also called magnetic moment. It measures the tendency of an object to align in a magnetic field. It is produced due to the spin angular moment of electrons or due to motion of electrons in a closed loop.
From the equation of magnetic dipole moment, it is clear that magnetic dipole moment is directly proportional to current in loop and to area of the loop. Therefore, we can eliminate option (A) and option (B).
We know that area is a vector quantity and direction of area vector is always perpendicular to the plane of the loop. Therefore, we can say that the magnetic dipole moment of a current carrying loop is directly proportional to the magnitude of area and it will have the same direction as that of the area vector since current is a scalar quantity and magnetic dipole moment is a vector quantity.
Therefore, the answer is option (D)



Thus, the correct option is D.



Note:Current does have both the magnitude and direction but it is considered as scalar quantity since it doesn’t obey the vector law of addition. That is why we don’t consider the direction of current when we say the direction of the magnetic dipole moment.