Question

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.

Answer 1

Magnetic Field Around a Current-Carrying Straight Conductor

Diagram Description:

• (A) Draw a straight vertical line segment to represent the straight conductor.
• (B) Mark an arrow along this conductor to indicate the direction of current (e.g., upwards). Label it Current (I).
• (C) Around the conductor, draw multiple concentric circles in a plane perpendicular to the conductor — these represent magnetic field lines.
• (D) On the circular lines, draw arrows showing the direction of the magnetic field. If current flows upwards, the magnetic field is anticlockwise (as seen from above), per the right-hand thumb rule.

Pattern of Magnetic Field Lines:

The magnetic field due to a straight current-carrying conductor forms concentric circles centered on the conductor. These field lines lie in a plane perpendicular to the conductor.

Direction of Current and Magnetic Field:

• Current (I): Direction must be shown on the conductor (arrow pointing up or down).
• Magnetic Field (B): Direction shown with arrows on concentric circles. Field direction is always tangential to the circle at any point.

Right-Hand Thumb Rule:

The direction of the magnetic field is determined by the Right-Hand Thumb Rule:

If you hold the current-carrying conductor in your right hand such that your thumb points in the direction of the current, then the direction in which your fingers curl around the conductor gives the direction of the magnetic field lines.

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.