A proton beam is going from north to south and an electron beam is going from south to north. Neglecting the earth's magnetic field, the electron beam will be deflected:

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

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. \(\dfrac{2\mu_{0} i}{\pi r}\)