Quiz 2 Flashcards
What is an electromagnet?
A non magnetic material that takes on the characteristics of a magnet whenever electrical current is passed through
Important date to remember?
Hans Christian Oersted, 1819
Left hand rule?
Point the thumb in the direction of electron flow and the fingers will wrap in the orientation of flow
Why are the lines of flux of a single conductor not useful?
They have no polarity and are too weak to be useful.
What are the two ways flux strength can be increased?
Increasing the current through the conductor, increasing the density of the lines of flux.
Flux density can be increased in what two ways?
By wrapping conductor in a coil, inserting a highly permeable core
what are the advantages to forming a coil?
The strength of the flux is increased , and gives the flux polarity
Left hand rule for coils?
Wrap the fingers of the left hand around the coil in the direction of electron flow, the thumb will point to the North Pole
In what two ways can the polarity of a coil be reversed?
Reverse the current flow through the conductor, reverse the direction of the wraps.
Measurements of flux?
Gilbert and amp turn
What is the advantage to having an electromagnet?
It has the characteristics of a natural magnet which can be controlled, both strength and polarity
Uses for electromagnets?
Relays, solenoids, generators, alternators, motors
Difference between a relay and a solenoid?
Relay uses a non movable core
What is a relay/solenoid?
An electrical switch which is operated by an electromagnet
What is the purpose of a relay?
To use a small amount of current to control a large amount of current
What is a generator/alternator?
A device which uses an electromagnet to generate electricity
Difference between a generator and an alternator?
In a generator the electromagnet does not spin
What is a motor?
A device in which two electromagnets with fields that repel each other and cause one of them to spin
What are the sources of electricity?
Magnetism, chemical, heat, pressure, light.
Example of magnetic power?
Alternator, generator
Example of chemical power?
Batteries
Example of thermal power?
Thermocouples
Example of pressure power?
Record needle
Example of light power?
Solar panels
What is the definition of a complete circuit?
An electrical circuit where there is a complete path from the source, to the load, and back to the source.
What is a source?
The part of the circuit that provides the potential for electron transfer.
What is a conductor?
The path by which electrons flow from the source, to the load , and back to the source.
What is the major consideration for choosing a material for a conductor?
Weight versus resistance
What are factors effecting resistance?
Resistivity, positive temperature coefficient of resistance, dimension of the conductor.
What is the cross sectional area of a conductor given in?
Circular mils.
Formula for circular mils?
a=D^2
What is the conversion between square mils and circular mils?
.7854
Square to circular divide by .7854
What is a load?
Any device designed to drop voltage
What is the purpose of switches?
To control the routing of electron flow.
Switch classifications?
SPST, SPDT, DPST, DPDT.
Types of switches?
Toggle, slide, rocker switch, wafer switch
What is the purpose of precision and micro switches?
Activated by mechanical means, to show position.
What is the purpose of protective devices?
To protect the wiring from excessive current
What is a fuse?
A fusible like with a low melting point alloy
What is a normal blow fuse?
Opens as soon as the excess current condition is exceeded
What is a slow blow fuse?
A fuse designed to allow the rated current to be exceeded for a short period of time before the fuse opens
Three types of circuit breakers?
Automatic resetting circuit breaker, manual setting circuit breaker, trip free circuit breaker
What is the only
Type of circuit breaker approved for aviation?
Trip free circuit breaker
Types of controlling mechanisms for circuit breakers?
Thermal and magnetic.
What is the purpose of resistors?
They are used in some applications to control voltage and in some applications to control current.
How does a resistor dissipate power ?
In the form of heat
Types of resistors?
Variable and carbon resistor.
Rheostat?
One circuit
Potentiometer?
Two circuits.
Types of carbon resistor?
Axial load and radial load resistor
How is the nominal value of a carbon resistor given?
By the color bands based on codes established by the electrical industries associates
Axial lead resistor designations?
1st band, 1st significant digit 2nd band, 2nd significant digit 3rd band, number of zeros (multiplier) 4th band, the tolerance. If no fourth band, tolerance is 20%
Radial lead resistor designations?
Body color- first significant digit
Large band- second significant digit
Dot- the number of zeros
Stripe- the tolerance
In a carbon resistor what determines the resistance rating in ohms?
The composition and the size determines the wattage rating
What is a wire wound resistor?
A special type of resistor designed to dissipate large amounts of power
What is a film resistor?
A special kind of resistor designed to dissipate very small amounts of power
What is an open circuit?
A circuit where there is not a complete path from the source through the load and back to the source
What is a logic circuit?
A binary circuit with one of two outcome possibilities
Name the types of logic circuits
AND OR NAND NOR EXCLUSIVE
OR
Black?
0, -
Brown?
1,1
Red?
2,2
Orange?
3,3
Yellow?
4,4
Green?
5, .5
Blue?
6, .25
Violet?
7, .1
Gray?
8, -
White?
9, -
Gold?
-, 5
Silver?
-, 10
No color?
0, 20
