Download presentation

Presentation is loading. Please wait.

1
Currents and Magnetism Textbook Sections 22-4 – 22-7 Physics 1161: PreLecture 13

2
Force of B-field on Current + v Force on 1 moving charge: –F = q v B sin( ) –Out of the page (RHR) Force on many moving charges: –F = (q/t)(vt)B sin( ) = I L B sin( ) –Out of the page! v L = vt B I = q/t ++++

3
Net force on loop is zero. Look from here But the net torque is not! Torque on Current Loop in B field A B C D B I X F F A B C D F F The loop will spin in place!

4
Torque on loop is = 2 x (L/2) F sin( ) = ILWB sin( ) Force on sections B-C and A-D: F = IBW (length x width = area) LW = A ! Torque is = I A B sin( ) W L A B C D B I X F F Torque on Current Loop in B field A B C D F F L/2

5
Torque tries to line up the normal with B! (when normal lines up with B, =0, so =0! ) Even if the loop is not rectangular, as long as it is flat: = I A B sin (area of loop) Magnitude: = I A B sin Direction: N # of loops A B C D B normal F F Torque on Current Loop between normal and B

6
Currents Create B Fields Lines of B Here’s a current- carrying wire. Current I OUT of page. Right-Hand Rule, 2 Thumb: along I Fingers: curl along B-field lines r = distance from wire r Magnitude of B a distance r from (straight) wire: B

7
Right Hand Rule 2 wire I Fingers give B!

8
Force between current-carrying wires I towards us B Another I towards us F Conclusion: Currents in same direction attract! I towards us B Another I away from us F Conclusion: Currents in opposite direction repel! Note: this is different from the Coulomb force between like or unlike charges.

9
Comparison: Electric Field vs. Magnetic Field ElectricMagnetic Source ChargesMoving Charges Acts on Charges Moving Charges Force F = Eq F = q v B sin( ) Direction Parallel EPerpendicular to v,B Field Lines Opposites Charges AttractCurrents Repel

10
Magnetic Fields of Currents http://hyperphysics.phy- astr.gsu.edu/hbase/magnetic/magfie.html#c1http://hyperphysics.phy- astr.gsu.edu/hbase/magnetic/magfie.html#c1

11
B Field Inside Solenoids Magnitude of Field anywhere inside of solenoid : B= 0 n I Right-Hand Rule 3 gives Direction: Fingers – curl around solenoid in direction of I Thumb - points in direction B == n is the number of turns of wire/meter on solenoid. = 4 x10 -7 T m /A (Note: N is the total number of turns, n = N / L) Magnetic field lines look like bar magnet! Solenoid has N and S poles!

12
B Field Inside Solenoids Magnitude of Field anywhere inside of solenoid : B= 0 n I Right-Hand Rule for loop/solenoid Fingers – curl around coil in direction of conventional (+) current Thumb - points in direction of B along axis n is the number of turns of wire/meter on solenoid. = 4 x10 -7 T m /A (Note: N is the total number of turns, n = N / L) Magnetic field lines look like bar magnet! Solenoid has N and S poles!

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