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Alternating Current, Generators, and Motors. Three Ways to Induce a Current. Changing the magnetic field strength Change the orientation of the loop with respect to the magnetic field Moving the circuit loop in or out of the magnetic field Generator
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Three Ways to Induce a Current • Changing the magnetic field strength • Change the orientation of the loop with respect to the magnetic field • Moving the circuit loop in or out of the magnetic field • Generator • Mechanical device that can move the circuit loop • Mechanical energy in the form of rotational motion
Generators • Generators produce constantly changing emf • Induced emfis 0 when loop is perpendicular to the field • Induced emf is at maximum when loop is parallel to the field
Maximum EMF for a Generator • Derived from Faraday’s law of induction • Max emf = NABw • w - angular velocity • w = 2pf
Alternating Current • EMF alternates from positive to negative • Output changes in direction at regular intervals • In the US, frequency of rotation for commercial generators is 60 Hz
rms current • The amount of direct current that dissipates as much energy in a resistor as an alternating current does in one cycle • Irms = 0.707 Imax • DVrms = 0.707 DVmax
Converting AC to DC • Split slip ring (commutator) converts alternating to direct current • When the current has dropped to 0 and is about to change direction the brush comes into contact with the other half of the commutator
Motors • Convert electrical energy to mechanical energy • Parts • Armature • Commutator • Brushes • Axle • Field magnet • DC power supply