Currents through Magnetic Fields

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Currents through Magnetic Fields

Today we discussed currents (in a straight wire and in a circuit) through a uniform magnetic field.

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The University of Vermont
Phys 012 - Elementary Physics
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Lecture 12 Outline of Last Lecture I. Magnetic Fields a. Magnets have two poles: north and south. b. Like poles repel, opposites attract. c. No magnetic monopoles have been found. d. Magnetic fields exist near moving charge. e. Field lines come out of north and go to south poles. f. Magnetic field at a point is tangent to field line (B). II. Earth’s Magnetic Field a. Geographic north is magnetic south (but this switches every couple ten thousand years). b. Compass will point in direction of magnetic field lines (ie. geographic north). c. Magnetic north is a few degrees off of “true north.” III. Magnetic Force a. Electric charges moving in a magnetic field can feel a force. i. F = qvB sinθ 1. v = velocity 2. B = magnetic field strength in teslas (T) = (N*s)/(C*m) 3. θ = angle between v and B if they are tail to tail b. Force is always perpendicular to v and B. c. Movement of a particle in magnetic field will be circular. i. ΣF = qvBsinθ = mac ii. sin (90°) = 1 iii. ac = v2/r iv. qvB = mac v. qvB = mv2/r vi. r = mv/qB d. Right-hand Rule: i. 1. Hold right hand so fingers point in the direction of v (opposite direction if charge is negative) ii. 2. Bend fingers in direction of B. iii. 3. Thumb will be pointing in direction of F. iv.  vector going toward you v.  vector going away from you IV. Magnetic Force versus Electric Force a. FE acts along direction of E field b. FB acts perpendicular to B field c. FE acts on stationary or moving charges d. FB acts on moving charges only e. FE does work in displacing a charged particle f. FB from steady doesn’t do work PHYS 012 1st Edition

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