Consider the situation shown in the figure. The straight wire is fixed but the loop can move under magnetic force. The loop will:

         

1.	remain stationary
2.	move towards the wire
3.	move away from the wire
4.	rotate about the wire

A charged particle is moved along a magnetic field line. The magnetic force on the particle is:

A moving charge produces:
1. electric field only
2. magnetic field only
3. both of them
4. none of them

Two parallel wires carry currents of \(20 ~\text A\) and \(40 ~\text A\) in opposite directions. Another wire carrying a current antiparallel to \(20 ~\text A\) is placed midway between the two wires. The magnetic force on it will be:
1. towards \(20 ~\text A\)
2. towards \(40 ~\text A\)
3. zero
4. perpendicular to the plane of the currents

Two parallel, long wires carry currents \(i_1,\) and \(i_2\) with \(i_1 > i_2.\) When the currents are in the same direction, the magnetic field at a point midway between the wires is \(10~\mu \text T.\) If the direction of \(i_2\) is reversed, the field becomes \(30~\mu \text T.\) The ratio of their currents \( i_1/i_2\) is:
1. \(4\)
2. \(3\)
3. \(2\)
4. \(1\)

Consider a long, straight wire of cross-sectional area \(A\) carrying a current \(i.\) Let there be n free electrons per unit volume. An observer places himself on a trolley moving in the direction opposite to the current with a speed \(v=\frac{{i}}{{n}{Ae}}\)and separated from the wire by a distance \(r.\) The magnetic field seen by the observer is very nearly;

1. \(\dfrac{\mu_{0} i}{2 \pi r}\) 
2.  Zero
3. \(\dfrac{\mu_{0} i}{ \pi r}\) 
4. \(\dfrac{2\mu_{0} i}{\pi r}\) 

The magnetic field at the origin due to a current element \(i.\vec{dl}\) placed at a position \(\vec r\) is:
(a). \(\frac{\mu_{0} i_{}{}}{4 \pi} \frac{d\vec{l} \times \vec{r}}{r^{3}}\)
(b). \(-\frac{\mu_{0} i_{}{}}{4 \pi} \frac{\vec{r} \times d\vec{l}}{r^{3}}\)
(c). \(\frac{\mu_{0} i_{}{}}{4 \pi} \frac{\vec{r} \times d\vec{l}}{r^{3}}\)
(d). \(-\frac{\mu_{0} i_{}{}}{4 \pi} \frac{d\vec{l} \times \vec{r}}{r^{3}}\)

Choose the correct option: 
1. (a), (b)
2. (b), (c)
3. (c), (d)
4. (a), (d)

Consider three quantities; \(x = E/B,\) \(y = \sqrt{1 / \mu_{0} \varepsilon_{0}},\) and \(z=\frac{ l }{ CR}.\) Here, \(l\) is the length of a wire, \(C\) is a capacitance and \(R\) is resistance. All other symbols have standard meanings. 

Choose the correct option from the given ones.

A long, straight wire carries a current along the \(z-\)axis. One can find two points in the \(X-Y\) plane such that:

Choose the correct option :

A long, straight wire of radius \(R\) carries a current distributed uniformly over its cross-section. The magnitude of the magnetic field is:

Choose the correct option from the given ones: