MOVING CHARGES AND MAGNETISM — Physics STD 12 Science — Question

→Oersted observed that a current in a straight wire caused deflection in a nearby magnetic compass needle.
→As shown in the figure (a), the wire is perpendicular to the plane of the paper. Electric current is emerging out of the plane of the paper.
→In this condition, the alignment of the needle is tangential to an imaginary circle which has straight wire as its centre and plane perpendicular to the wire.
→Here, since the current passing through the wire is relatively large, the resulting magnetic field is relatively strong, so the Earth's magnetic field can be neglected.
→As shown in figure (b), by reversing the direction of the current (going in to the plane of paper)the orientation of the needle is also reversed.
→The deflection of needle increases on increasing the current or bringing the needle closer to the wire. it indicates that the magnetic field increases in magnitude.
→As shown in figure (c). If iron ear fillings sprinkled around the wire arrange themselves in concentric circles with the wire as the centre.
→From all of these experiments, Oersted concluded that moving charges or currents produced a magnetic field in the surrounding space.