Relating Magnetic and Electric Forces

Relating Magnetic and Electric Forces - multiple moving...

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Relating Magnetic and Electric Forces Using the definition of the magnetic field we have just developed, we become able to generate a complete expression for the force exerted on a charged particle, q , in the presence of both electric and magnetic fields. Recall that in the presence of an electric field alone the force felt by a point charge q is simply proportional to the field at that point, or F = qE . Thus, if this point charge is in the presence of both an electric field and a magnetic field, we can find the total force on the charge by simple vector addition: = q + This equation only applies to vector quantities--usually the force due to the electric field and the magnetic field are not in the same direction, and cannot be added algebraically. Magnetism and Currents We now move on from examining magnetism on a single charge, to magnetism in relation to
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Unformatted text preview: multiple moving charges, or currents. Magnetic Force on a Current Though it was simplest to define the magnetic field in terms of the force on a single moving charge, it is nmore common to encounter a current-carrying wire in the presence of the magnetic field. To find the force on such a wire we simply need to remember the equation for current: I = , or that the current is the amount of charge passing through a given point in a period of time. We may thus substitute It for q in our equation, our force equation: F = = = where L is the length of wire with the current running through it. Many times, however, the wire will be very long and we'll want to know the force per unit length. To do so we simply divide both sides of the equation by L : = From this equation we will be able to see many properties of magnetic field...
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This note was uploaded on 02/09/2012 for the course PHY PHY2053 taught by Professor Davidjudd during the Fall '10 term at Broward College.

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