What is the magnetic dipole moment of the given loop?

The magnetic moment of a current (i) carrying circular coil of radius (r) and number of turns (n) varies as :

1. $1/r^2$                            

2. $1/r$

3. r                                  

4. $r^2$

A small coil of N turns has an effective area A and carries a current I. It is suspended in a horizontal magnetic field $\stackrel{.}{B}$ such that its plane is perpendicular to $\stackrel{.}{B}$. The work done in rotating it by $180°$ about the vertical axis is 

1. $NAIB$                               2. $2NAIB$ 

3. $2\mathrm{\pi NAIB}$                           4. $4\mathrm{\pi }NAIB$

An electron moves with a constant speed v along a circle of radius r. Its magnetic moment will be (e is the electron's charge)

1. evr                       

2. $\frac{1}{2}$evr 

3. ${\mathrm{\pi r}}^2$ev                    

4. 2$\mathrm{\pi }$rev