A wire of length \(l\) carrying current \(i\) is folded to form a circular coil of \(N\) turns. What should be the value of \(N\) to have the maximum value of the magnetic moment in the coil?
1. \(1\)

2. \(4\)

3. \(9\)

4. \(10\)

If charge \(-Q\) is moving vertically upwards, then what will be the force on the charged particle if it enters a magnetic field that is pointed towards the south?
1. North
2. South
3. East
4. West

What happens when the number of turns in a galvanometer is doubled?

The two parts of the loop are circles of radii \(2a\) and \(a,\) respectively, and carry the same current \(i\) as shown in the given figure. What is the magnitude of the dipole moment of the current loop?

1. \(5 \pi a^{2}\hat i\) 
2. \(4 \pi a^{2}\hat i\) 
3. \(3 \pi a^{2}\hat i\) 
4. zero

What is the magnetic moment of the following current loop?
            
1. \(24~\text{Am}^2\)
2. \(12~\text{Am}^2\)
3. \(6~\text{Am}^2\)
4. zero

An electron and a proton are revolving around a common centre \(O\) in two coplanar circular paths as shown in the figure with a time period of rotation of \(1\) s and \(2\) s, respectively. What will be the net magnetic field at \(O\)?

                
1. \(\mu_{0} i_{1} i_{2}\)
2. \(\dfrac{\mu_{0} i_{1} i_{2}}{\pi}\)
3. \(\dfrac{\mu_{0} i_{1} i_{2}}{2 \pi}\)
4. \(2 \mu_{0} i_{1} i_{2}\) 

If a long hollow copper pipe carries a direct current along its length, then the magnetic field associated with the current will be: