what can you do with Magnetic Field and where does it come from!This weekPROBLEM Redux – review direction issue.Slide 4Force And WiresConsider TWO wiresmagnetic Field of a wire carrying a currenttwo wires againSome useful Equations not derived in the texttalk about torqueCurrent LoopThe Loop (From the top)The other sidesN Turns of WireApplication: The motormotorgeneratorSlide 18Slide 19Slide 20W10D1November 1, 2010Mostly magnetism and effects on and from currents.There is a new WA posted and another may be added at any time.Quiz on FridayNext examination is looming! keep up with the work.Magnetism3An electron at point A in the figure has a speed v0 of 1.4 x 106 m/s. Find (a)the magnitude and direction of the magnetic field that will cause the electron to follow the semicircular path from A to B and (b) the time required for the electron to move from A to B. m=9.1E-31 Kge=1.6E-19 CBqmvrmBq+Assume B into the pagevB is to the leftFBut q is negative and forcewill go the other way. Which is what we want!B is as assumed!The magnetic force on themoving charges pushes thewire to the right. Why??v FIIThe two wires willA AttractB RepelC Neither of the aboveD Insufficient InformationxxxxxxxxxxxxvX BF02IBrmp=F BIL=Not the same B!!704 10 / permutivity of free space (vacuum)T m Am p-= � � =0 12IBDmp=D{ }0 1 0 1 222 2I I I LF BIL I LD Dm mp p� �= = � =� �� �00022IBrIB NRB nImpmm===Field a distance r from a wireField at the center of a loopof wire with N turnsField inside a solenoid with nturns per unit lengthCurrent Loops in Magnetic FieldsCurrent Loops in Magnetic FieldsMagnetism11Loop will tend to rotate due to the torque the field applies to the loop.What is forceon the ends??Magnetism 12pivotOBSERVATIONForce on Side 2 is outof the paper and that onthe opposite side is into the paper. No net forcetending to rotate the loopdue to either of these forces.The net force on the loop is also zero,Magnetism 131=F1 (b/2)Sin() =(B i a) x (b/2)Sin()total torque on the loop is: 21Total torque:=(iaB) bSin() =iABSin()(A=Area)=NiABSin()N Turns If the conductor is a loop, the torque can create an electric motor.MANY TURNSOF WIREMotors are usually
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