why magnetic feild is created around a conductor when current is passed through it?

When a charged particle—such as an electron, proton or ion—is in motion, magnetic lines of force rotate around the particle. Since electrical current moving through a wire consists of electrons in motion, there is a magnetic field around the wire.
This field can be demonstrated by placing fine iron filings or shavings on a car and sticking a wire through the middle of the card. When a DC electrical current is passed through the wire, the iron filings align to show the magnetic field.
Iron filings show magnetic field around electric wire