Draw the pattern of magnetic field lines due to a current carrying straight conductor. Mark on it the direction of current in the conductor and the direction of the magnetic field developed. Name the rule that helps us to determine the direction of magnetic field lines in this case.

Question

Two identical circular loops \(P\) and \(Q\) each of radius \(r\) are lying in parallel planes such that they have common axis. The current through \(P\) and \(Q\) are \(I\) and \(4I\) respectively in clockwise direction as seen from \(O\). The net magnetic field at \(O\) is:

Answer 1

Magnetic Field of a Straight Current-Carrying Wire

Magnetic Field Around a Current-Carrying Straight Conductor

Diagram Elements:

(A) Represent the wire with a straight vertical line.
(B) Indicate current direction (e.g., upwards) with an arrow and label it Current (I).
(C) Draw concentric circles around the wire, in a plane perpendicular to it, to represent magnetic field lines.
(D) Show the magnetic field direction with arrows on the circles. If the current is upwards, the field is anticlockwise (viewed from above), according to the right-hand thumb rule.

Magnetic Field Line Pattern:

A straight, current-carrying wire generates a magnetic field composed of concentric circles centered on the wire. These field lines lie in a plane perpendicular to the wire.

Current and Magnetic Field Directions:

Current (I): Show the direction on the wire using an arrow (up or down).
Magnetic Field (B): Show the direction with arrows along the circular field lines. The field direction is always tangential to the circle at any point.

Right-Hand Thumb Rule:

The Right-Hand Thumb Rule determines the magnetic field direction:

Grasp the current-carrying wire with your right hand, so your thumb points in the current's direction. Your curled fingers then indicate the magnetic field's direction.

Summary:

\[ \begin{array}{|l|l|} \hline \textbf{Property} & \textbf{Description} \\ \hline \text{Field Lines} & \vec{B} \text{ are concentric circles around conductor} \\ \text{Direction Rule} & \text{Right-Hand Thumb Rule} \\ \text{Rule Statement} & \text{Thumb } \parallel \text{Current (I)}, \text{Fingers } \parallel \vec{B} \\ \hline \end{array} \]

Note: A labeled diagram showing a vertical conductor, current direction (upward), and anticlockwise circular magnetic field lines should be placed here.