A current-carrying straight wire is kept along the axis of a circular loop carrying a current. The straight wire

1.	will exert an inward force on the circular loop
2.	will exert an outward force on the circular loop
3.	will not exert any force on the circular loop
4.	will exert a force on the circular loop parallel to itself

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:

A circular loop is kept in that vertical plane which contains the north-south direction. It carries a current that is towards the north at the topmost point. Let A be a point on the axis of the circle to the east of it and B a point on this axis to the west of it. The magnetic field due to the loop:

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

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. \(\dfrac{2\mu_{0} i}{\pi r}\) 

A current element \(i\overrightarrow{dl}\) is placed at position \(\vec r\) from the origin. What is the magnetic field \(\overrightarrow{dB}\) at the origin due to this current element?

Choose the correct option from the given ones: