A wire carrying electric current will produce a magnetic field with closed field lines surrounding the wire.

Another version of the right hand rules can be used to determine the magnetic field direction from a current—point the thumb in the direction of the current, and the fingers curl in the direction of the magnetic field loops created by it. See.

The Biot-Savart Law can be used to determine the magnetic field strength from a current segment. For the simple case of an infinite straight current-carrying wire it is reduced to the formB=μ0I2πrB=μ0I2πr.

A more fundamental law than the Biot-Savart law is Ampere ‘s Law, which relates magnetic field and current in a general way. It is written in integral form as∮B⋅dl=μ0Ienc∮B⋅dl=μ0Ienc, where Iencis the enclosed current and μ0is a constant.

A current-carrying wire feels a force in the presence of an external magnetic field. It is found to beF=BilsinθF=Bilsinθ, where ℓ is the length of the wire, i is the current, and θ is the angle between the current direction and the magnetic field.