Question

Magnetic dipole moment is a:
A. Scalar quantity
B. Vector quantity
C. Constant quantity
D. None of these

Answer 1

Hint: Try to understand the concept of scalar and vector quantity. Try to imagine if a physical quantity has both the direction and magnitude or it has only magnitude not direction. This way you can find your answer.

Complete step by step answer:
Scalar quantity can be defined as a physical quantity which has only magnitude, not direction.
A vector quantity can be defined as a physical quantity which has both the magnitude and direction.
Consider the following example.

If we travel from point A to point B. the distance will be 40 km. It has only magnitude. Next if we move backward to point C the total distance travelled is $40+20=60km.$ So, distance has only the magnitude, not a direction. So, distance is a scalar quantity.
Now, if we consider displacement it will give the real distance between the points A and C with the direction from A to C. The displacement will be 20 km in the direction A to C. So, displacement is a vector quantity.
A magnetic dipole can be defined as the magnetic north pole and the magnetic south pole separated by a small distance.
Magnetic moments can be defined as the quantity that can give the strength or orientation of a magnet. This magnetic dipole moment can also be described as the component of magnetic moment. The dipole magnetic moment of a bar magnet can also be described as the product of pole strength and the magnetic length.
Unit of magnetic moment is Ampere-meter squared $\left( A{{m}^{2}} \right)$. Its dimension is $\left[ {{L}^{2}}A \right]$.
If dipole moment is a vector quantity for a bar magnet the direction of the dipole moment is from south pole to north pole.
So, we can say that magnetic moments have magnitude as well as a direction. Hence, magnetic dipole moment is a vector quantity.
The correct option is (B).

Additional information:
If we consider a current carrying coil it will also behave like a magnet. Magnetic dipole moment of the current carrying coil is,
$\mu =NiA$
Where N is the number of turns of the coil, i is the current and A is the area of the coil.
Here direction of the magnetic moment is determined by right hand thumb rule.

Note: Considering the bar magnet as a current loop the direction of the dipole moment will be from south pole to north pole of the magnet. Hence, the other options are invalid.
The unit for dipole moment in SI unit is ampere-square metre.