Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
To find the direction of the magnetic field, we apply the right-hand thumb rule. According to this rule, if we hold the current-carrying conductor in our right hand such that the thumb points in the direction of current, then our fingers wrap around the conductor in the direction of the magnetic field lines.
Since the current in the circular loop flows clockwise (when viewed from above the table), we curl the fingers of our right hand in the clockwise direction. This makes the thumb point downwards, perpendicular to the plane of the table. Therefore, inside the loop, the magnetic field is directed downwards (into the plane of the table).
Outside the loop, the magnetic field lines are in the opposite direction. Hence, the magnetic field outside the loop is directed upwards (out of the plane of the table).
Explanation
The textbook explains that for a current-carrying circular loop, every section of the wire contributes to the magnetic field lines in the same direction within the loop. By applying the right-hand thumb rule, when current flows clockwise, the magnetic field inside points downward (into the table), while outside it points upward. This is consistent with the principle that magnetic field lines form closed loops.
Solution Steps
Step 1: Identify the direction of current in the loop (clockwise when viewed from above).
Step 2: Apply the right-hand thumb rule - curl fingers in the direction of current.
Step 3: Observe the direction of thumb - it points downward, indicating magnetic field direction inside the loop.
Step 4: Outside the loop, magnetic field direction is opposite to that inside.