Magnetic Field due to a CurrentCarrying Wire Physics

Magnetic Field due to a Current-Carrying Wire Physics Mrs. Coyle

A Current-Carrying Wire Causes a Magnetic Field Around it.

Hans Christian Oersted, 1820

Right Hand Curl Rule

Magnetic Fields of Long Current-Carrying Wires B = mo I 2 p r I = current through the wire (Amps) r = distance from the wire (m) mo = permeability of free space = 4 p x 10 -7 T m / A B = magnetic field strength (Tesla) I

Example 1 • What is the magnitude of the magnetic field created by a 0. 25 A current at a distance of 50 cm from the wire? • Answer: 1 x 10 -7 Tesla

Magnetic Field of a Current Carrying Wire • http: //www. walterfendt. de/ph 14 e/mfwire. htm

Magnetic Field in the Center of a Current-Carrying Loop (Ring) B = mo I 2 r

Note • The overall shape of the magnetic field of the circular loop is similar to the magnetic field of a bar magnet.

Magnetic Field at Center of a Solenoid B = mo NI L N: Number of turns L: Length n=N/L ------------L--------

Force of Attraction Between Two Long Current-Carrying Wires F= mo I 1 I 2 L 2 p d d : distance between wires I : current L: length of wire

Note • If the wires have currents in opposite directions, the wires repel each other.

Example 2 • What is the force of attraction felt by two 4 m long current-carrying wires carrying currents of 2 A and 3 A, that are 60 cm from each other? • Answer: 8 x 10 -6 N