Based physics II Lecturer Mr.syuhendri, M.Pd. MAGNETIC FIELD BY THE FLOW LISTRIK Nine Group Intan Megawati Putri Marisa Dian Irawan@copyright by nine group basic physic II
DIAGRAM MATERIAL II. BY FIELDI. Biot Savart Law magnetic dipole IV.FORCE BETWEEN TWO STRAIGHT WIRE-flowingIII. AMPERE’S LAW parallel
I. Biot Savart Law Hans Christian Oersted in 1819 has been observed that a compass needle would deviate him if placed near an electrical current. This shows that the electric currents affect the direction maget field, so the electric current causes a magnetic field. From the Biot and Savart experiment in 1820 found that the magnetic fields around electric current can be formulated as follows: I dl Ѳ P µ0 = permeability of vacuum r = 4π x 10-7 Wb A-1 m-1 = 4π x 10-7 Tm A-1 The direction of dB is perpendicular both to the dl, or against the r.
Biot Savart formulation with vector notation is : I p Ѳdl r d Bp r2 r1 p1 I P2
=iMagnetic field formed by a loop current. Magnetic field by a circular loop on the axis ofHere we will see an equal influence the circle, in the image above is to point P1:magnetic dipole (on the magnetic field)with electric dipole effect (on theelectric field). Directions Bp1 is unidirectional A. For a very distant point P, x > P, then R2 + x2 = x2 so that the magnetic field in P1 expression can be written as follows: ,m iA
are: The results we get above a lot like the electric field generated by an electric dipole: The electric field at P by the electric dipole The electric field at P by the electric dipole p qd By analogy to the dipole magnetic and electric fields that result, we consider an arbitrary point, for example P2. The magnetic field in P2 by a magnetic dipole m are:
So, is defined magnetic dipole associated with the current in a closed loop,namely: m Magnetic dipole m iA magnitude A is the loop cross-sectional area, A is the appropriate direction of screw rotation direction of flow.
However, Amperes law can only be used at currents that generate the magneticfield with a certain symmetry. For example on a very fast-flowing straight wirelength: B IWe know that the magnetic field surrounding a long straight wire-flowing istrending in the direction of rotation as the screws (see picture) and thesame amount at every point, a distance equal to the wire. Because it is sothat, to choose a closed path sectional area of a circle that isperpendicular to the wire circle and centered on the wire. B dl I
We apply the Law of amperes as follows: · ¤ dl is an element in the circular trajectory, the direction of dl is selected equal to B so that B.dl = Bd ¤ Iin is the current which is surrounded by a closed path that we choose. thus , because B is constan From the results , It appears that B is inversely proportional to r and the results are in accordance with the Law of Biot Savart. So, B
There are two wires have current, respectively bring currents I and I in the same direction. I I x x x x x x by wire (1) B x x (1) (2)Wire (1) will cause B field around it. On the wire (2), there are positive charges flow inthe direction of the current direction I, or the flow of negative charge in the oppositedirection I. wire (2) will get a magnetic force towards the wire (1), a big force of unitylength: