Meters and Motors with magnetism

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.

Galvanometer If it is calibrated for amps it is an ammeter, if for volts it is a voltmeter

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.

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.

DC motor

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

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

 pg 736  16-17; 28-35