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Published byAmice Craig Modified over 8 years ago
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Meters and Motors with magnetism
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Measuring electric current A galvanometer can be used to measure current in a wire. This is made of a solenoid and a thin magnetic needle. The thin magnet is held in one direction by a spring, and placed on the solenoid. The solenoid is arranged so when turned on the magnetic field will pull the needle against the spring.
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Galvanometer If it is calibrated for amps it is an ammeter, if for volts it is a voltmeter
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Motor A galvanometer works similar to the way a DC motor works. Motor- coverts electrical energy into kinetic (rotational) energy A galvanometer will make a half rotation, a motor must simply continue this process and make several complete rotations.
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DC motor Place a solenoid loop in between two permanent magnets. Supply current to the solenoid that the attraction/repulsion will rotate the solenoid Have the rotation disconnect the solenoid from the power source in ¼ of a turn In the next ¼ of a turn have the power source reconnect so that current will flow in the opposite direction.
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DC motor
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Bottom view of contact point Stationary contact points for electric current Rotating brushes connected to solenoid loop and complete the circuit Insulators that opens the circuit
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View of solenoid loop through magnets northSouth Current through solenoid N S northSouth Loop rotates ¼ turn then no current. Momentum carries it northSouth ¼ later it is reconnected in the opposite directions N S northSouth Loop rotates ¼ turn then no current. Momentum carries it Now we are back here Motor in action
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pg 736 16-17; 28-35
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