lecture20 - Sources of Magnetic Fields Sources Be s m tic...

Info iconThis preview shows pages 1–14. Sign up to view the full content.

View Full Document Right Arrow Icon
Sources of Magnetic Fields Sources of Magnetic Fields
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Besides magnetic poles, electric currents create magnetic fields. There are two ways of calculating B produced by currents: i) Biot-Savart Law : Field of a “current element” (analogous to a point charge in electrostatics). i) Ampère’s Law : An integral theorem similar to Gauss’s law.
Background image of page 2
m/A T 10 4 7 o × = - π μ ˆ 4 2 o r I r ds dB × = We get the total B by integrating ds along the wire : (“permeability of vacuum”) I I θ ds dB ˆ 4 2 o × = r I r ds B Biot-Savart Law Biot-Savart Law
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Quiz When is d B =0 ? How does d B vary with r ? Current I in a straight wire What is the direction of B at points a and b ? a b
Background image of page 4
Example 1 Example 1 Find B at a distance R from a long straight wire x y I R φ dx dB θ i ds ˆ = dx direction) - z (in o dx r I dB 2 sin 4 θ π μ = (note sin = R/r = cos θ ) r
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Solution
Background image of page 6
Result : the magnitude of the field produced at a distance R from a long straight wire is: R I B π μ 2 0 = I The field lines form circles around the wire. Note the right-hand rule.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 8
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 10
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 12
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 14
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/13/2011 for the course PHYSICS Physics 1E taught by Professor Venus during the Winter '03 term at McMaster University.

Page1 / 14

lecture20 - Sources of Magnetic Fields Sources Be s m tic...

This preview shows document pages 1 - 14. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online