# lec10 - How a DC Motor works • The torque on a...

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Magnetic Force on Currents Magnetic field exerts a force on a current similar to the force on a moving charge. On a straight current-carrying wire The magnetic force ( F ) is directed perpendicular to the plane formed by the current ( I ) and the magnetic field ( B ). the direction of the force follows RHR -1 . On a current-carrying coil The magnetic forces on the sides produce a net torque φ τ sin NBIA = F r F r Top View A - area of coil N - number of turns φ - angle between normal and B

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Unformatted text preview: How a DC Motor works • The torque on a current-carrying coil in a magnetic field makes the coil turn (causes a rotational acceleration). • The rotation will not persist because the torque reverses its direction when the coil rotates beyond φ =0 (or 180 ) • In a DC motor, sliding contacts (between the battery leads and the rotating coil) are used to reverse the current in the coil every half turn, thus maintaining the same torque direction. 1 2 1 2 1 2...
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## This note was uploaded on 12/06/2011 for the course PHYSICS 111&112 taught by Professor Unknown during the Spring '11 term at Ohio State.

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lec10 - How a DC Motor works • The torque on a...

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