CBSE Class 10 Science 2019 · Paper 31/5/2 · Question 7

Pattern (see the figure): the magnetic field lines are concentric circles on the cardboard, centred on the conductor, closer together near the conductor and farther apart away from it. Right-hand thumb rule: Imagine that you are holding the current-carrying straight conductor in your right hand so that the thumb points in the direction of the current; then the fingers wrapped round the conductor give the direction of the magnetic field lines. Use in this case: the current is vertically downwards, so point the right thumb downwards along the conductor. Seen from above the cardboard the fingers curl clockwise, so the magnetic field lines are concentric circles in the clockwise direction (when seen from above).