Download presentation

Presentation is loading. Please wait.

Published byAdam O’Connor’ Modified over 4 years ago

1
Electromagnet

2
Wire Field A moving charge generates a magnetic field. Symmetry with experiencing force Perpendicular to direction of motion Circles around path Outside a straight wire the magnetic field is cylindrical. Decreases inversely with distance I B

3
Permeability The permeability defines the strength of the B field in a material. The vacuum permeability is 0. Defined as 0 = 4 x 10 -7 T m / ADefined as 0 = 4 x 10 -7 T m / A The permeability is constant for most materials. Usually close to 0Usually close to 0 Not constant for ferromagnetic materials like iron > 0Not constant for ferromagnetic materials like iron > 0

4
Mutual Attraction Two parallel wires with current will exert a force on each other. Wire length l Separation d Currents in the same direction attract. Currents in the opposite direction repel. I1I1 d I2I2 l

5
Wire Force Find the force per unit length experienced by each of two long parallel wires in avacuum separated by 1.0 m carrying currents of 1.0 A. This is the official definition of the SI unit of the ampere (A). 1 A = 1 C/s1 A = 1 C/s Convert the force on the wire into a force per unit length. F/l = (4 x 10 -7 Tm/A)(1.0 A)2 / 2 (1.0 m) F/l = 2 x 10 -7 N/m The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross- section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10 -7 newton per meter of length.

6
Loop Field Each segment of a loop of current contributes a circular field. All the same direction inside loop Similar to a dipole pattern Field strength depends on radius of loop R.

7
Solenoid Multiple parallel loops form a solenoid. Each of N loops contributes a share of the fieldEach of N loops contributes a share of the field Solenoids create very uniform magnetic fieldsSolenoids create very uniform magnetic fields Tight, short coil

8
Close Loops Field in a solenoid varies at the edges from each loop of wire. Closer loops in a solenoid make a stronger field. Turns per length n = N/lTurns per length n = N/l Formula changes for a long coilFormula changes for a long coil A split coil would have half the field. Equivalent to saying half the field leaks out between loops.Equivalent to saying half the field leaks out between loops. B NI l

9
Electromagnet next An electromagnet is usually a solenoidal coil of wire. Increasing the permeability will increase the field lines. Iron core solenoid

Similar presentations

© 2020 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google