Give Oersted's observation.

Explanation

1. As shown in figure, conducting wire is connected with battery.

2. Magnetic needle is kept nearby conducting wire which is stable in North-South direction.
3. As key is closed, current in a straight wire caused deflection in a nearby magnetic compass needle and alignment of the needle is tangential of an imaginary circle which has the straight wire as its centre and has its plane perpendicular to the wire. This situation is depicted in figure (a). Here the needle is sufficiently close to the wire so that the Earth.s magnetic field may be ignored. Reversing the direction of the current reverses the orientation of the needle which is depicted in figure (b).
4. The deflection increases on increasing the current or bringing the needle closer to the wire.
5. Moving charges or currents produced a magnetic field in the surrounding space.