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 form B=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 Ienc is the enclosed current and μ0 is a constant.A current-carrying wire feels a force in the presence of an external magnetic field. It is found to be F=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.Key TermsBiot-Savart Law: An equation that describes the magnetic field generated by an electric current. It relates the magnetic field to the magnitude, direction, length, and proximity of the electric current. The law is valid in the magnetostatic approximation, and is consistent with both Ampère’s circuital law and Gauss’s law for magnetism.Ampere’s Law: An equation that relates magnetic fields to electric currents that produce them. Using Ampere’s law, one can determine the magnetic field associated with a given current or current associated with a given magnetic field, providing there is no time changing electric field present.
