A pickup coil is mounted on the axle support When the magnet passes over the

# A pickup coil is mounted on the axle support when the

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A pickup coil is mounted on the axle support When the magnet passes over the pickup coil, a pulse is generated A computer keep tracks of the number of pulses Section 21.7
Ground Fault Interrupters A ground fault interrupter (GFI) is a safety device used in many household circuits It uses Faraday’s Law along with an electromechanical relay The relay uses the current through a coil to exert a force on a magnetic metal bar in a switch Section 21.7
GFI, cont. During normal operation, there is zero magnetic field in the relay If the current in the return coil is smaller, a non-zero magnetic field opens the relay switch and the current turns off
Electric Guitars An electric guitar uses Faraday’s Law to sense the motion of the strings The metal string passes near a pickup coil wound around a permanent magnet As the string vibrates, it produces a changing magnetic flux The resulting emf is sent to an amplifier and the signal can be played through speakers Section 21.7
Generators, Motors and Cars Motors and generators provide examples of conservation of energy and the conversion of energy from one type to another A hybrid car contains two motors and a generator The hybrid car “recaptures” some of the energy normally converted to heat when braking and stores it in batteries A hybrid car is a practical example of the conversion between mechanical and electrical energy Section 21.7
Induction from a Distance Assume a very long solenoid is inserted at the center of a single loop of wire The field from the solenoid at the outer loop is essentially zero Section 21.8
Induction from a Distance, cont. The field inside the solenoid at the center of the loop still produces a magnetic flux through the inner portion of the loop Energy is transferred across the empty space between the two conductors The energy is carried from the solenoid to the outer loop by an electromagnetic wave Section 21.8

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• Fall '19
• Magnetic Field