Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Foundations > Basic Electricity > Flashcards

Basic Electricity Flashcards

1
Q

Describe the basic composition of an atom and the concept of electron flow

A

Electricity is electron flow through materials and devices. Atom Structure - Electron = negative charge
Proton = positive charge. Electrostatic force attracts electrons and protons. Electrons in motion try to pull away from nucleus. Atoms can lose or gain electrons. Atoms become either negatively or positively charged.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define electrostatic force

A

force that holds electrons in their orbits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define potential difference

A

how large the electrostatic force is between two charged objects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define electromotive force

A

the sum of the potential differences of all charged particles in the electrostatic field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define ion charge

A

Atoms that lose or gain one or more electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define Coulomb’s Law

A

Strength of the attraction or repulsion force between two charged objects, dependent upon two factors: Amount of charge on each object and Distance between the objects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define Conductor

A

Materials with electrons that are loosely bound to their atoms, or materials that permit free motion of a large number of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define Insulator

A

Materials with electrons that are tightly bound to their atoms and require large amounts of energy to free them from the influence of the nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define Resistor

A

Materials that conduct electricity, but offer opposition to current flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define Voltage

A

potential difference between charged objects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define Current or electron current flow

A

Movement of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Define conventional current flow

A

flow of positive charges through a conductor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Define direct current

A

flows continuously in same direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Define alternating current

A

periodically reverses direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Define real source

A

current or voltage supply that has some losses associated with it such as a battery or electrical generator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Define ideal source

A

theoretical concept of current or voltage supply (such as a battery) that has no losses and is a perfect voltage or current supply (used for analytical purpose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe Voltage

A

Electromotive force (EMF) that causes electrons to move in a conductor; measured in Volts; E=IR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe Current

A

Electron current, or amperage, is the movement of free electrons through a conductor; Measured in amps; I=E/R (The Indians saw the Eagles play over the River)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe Resistance

A

opposition to current flow; measured in ohms; R=E/I

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe Conductance

A

the ability to conduct current; measured in siemens; G=1/R

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe Power

A

Rate at which work is done, or the rate heat is generated; measured in Watts; P=I2R

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe Inductance

A

Ability of a coil to store energy, induce a voltage in itself, and oppose changes in current flow; measured in Henry(s)

23
Q

Describe Capacitance

A

Ability to store an electric charge; measured in Farads; C=Q/E (Q= amount of charge)

24
Q

Describe Frequency

A

Number of alternating voltage or current cycles completed per second; measured in Hertz (Hz)

25
Q

Define Magnetic Flux

A

Group of magnetic field lines emitted outward from north pole of a magnet.

26
Q

Define flux density

A

the amount of magnetic flux that passes through a certain area, perpendicular to the direction of magnetic flow

27
Q

Define permeability

A

Measure of ability of a material to form a magnetic field within itself; or degree of magnetization that material obtains in response to applied magnetic field

28
Q

Define magnetomotive force

A

strength of a magnetic field in a coil of wire

29
Q

Define reluctance

A

Opposition to the production of flux in material

30
Q

Describe Ferromagnetic – Nonmagnetic

A

Have the ferromagnetic properties of iron, Made of ceramic material. Relative permeability’s that range from 50 to 200 Commonly used in coils for RF (radio frequency) transformers.
Examples of ferromagnetic materials are iron, steel, nickel, cobalt, and the commercial alloys of alnico and peralloy

31
Q

Describe Paramagnetic

A

Have relative permeability of slightly more than one. Lose their magnetism when the magnetizing field is removed.
Examples of paramagnetic materials are aluminum, platinum, manganese, and chromium
diamagnetic.

32
Q

Describe the operation of a simple magnetic circuit including effects of hysteresis.

A

When a ferromagnetic material is magnetized in one direction, it will not relax back to zero magnetism when the imposed magnetic field is removed
Some magnetic domains remain aligned after the magnetic field removed. Called residual magnetism. Known as hysteresis or lagging behind. Energy to realign magnetic domains is hysteresis losses.

33
Q

schematic diagrams

A

the standard way to show information about electrical and electronics circuits. Component parts are represented by graphic symbols. With small symbols it is possible to have diagrams in a compact form. Symbols and associated lines show how circuit components are connected and relationship of components with one another.

34
Q

one-line diagrams

A

Components of a circuit using single lines and graphic symbols. Two or more conductors that are connected between components in the actual circuit. Information about the sequence of the circuit. Less detail than a schematic diagram. Highly complex systems without showing the actual physical connections between components and individual conductors.

35
Q

block diagrams

A

Show relationship between component groups, or stages in a circuit, including flow path through a circuit from input to output. Blocks are squares or rectangles connected by single lines with arrowheads at terminal end. Information to describe the stages of components is contained in the blocks

36
Q

Wiring Diagram

A

Simple method to show wiring connections in an easy-to-follow manner. Often included with home appliances and automobile electrical systems. Show the component parts in pictorial form. Components identified by name. Also show the relative location of component parts and color coding of conductors or leads

37
Q

protective relays

A

an automatic device which senses an abnormal condition and closes contacts.

38
Q

fuses

A

circuit protection device where the wire is smaller (capacity) than the conductor it protects and melts before the conductor is harmed.

39
Q

circuit breakers

A

breaks (opens) the circuit, when pre-determined conditions are sensed. Can also be operated manually to open a circuit.

40
Q

Describe the action of a current-carrying conductor in a magnetic field.

A

A force is applied to the conductor, which attempts to move conductor in a direction perpendicular to the magnetic field

41
Q

State the function of torque in a direct current motor and how it is developed.

A

Torque is the force which produces and maintains rotation
The sum of the forces, in Newtons, multiplied by the radius of the armature, in meters, is equal to the torque developed by the motor in Newton-meters (N-m)
Torque is the product of the force exerted on the rotor and the radius of the rotor.
The field strength, in part, determines force.

42
Q

Describe how Counter-Electromotive Force (CEMF) is developed and the function it performs in a DC motor.

A

Current to start the armature turning will flow in the direction determined by the applied DC power source. After rotation starts, the conductor cuts lines of force. By applying the left-hand rule for generators, the EMF that is induced in the armature will produce a current in the opposite direction. The EMF induced as a result of motor operation, is called counter-electromotive force, or CEMF

43
Q

Describe how the speed of a DC motor is adjusted, the relationship between field current and induced voltage, and the relationship between armature current and torque produced in a DC motor.

A

The field of a DC motor is varied using external devices, usually field resistors. With a constant voltage applied to the field (E), as the resistance of the field (RF) is lowered, the amount of current flow through the field (IF) increases. An increase in field current will cause field flux (ΦF) to increase. Conversely, if the resistance of the field is increased, field current and field flux will decrease. If the field flux of a DC motor is decreased, the motor speed will increase.

44
Q

Describe why starting resistors are necessary for large DC motors.

A

At the moment a DC motor is started, rotor (armature) is stationary and there is no counter EMF being generated.
To reduce the high starting current, an external resistance is placed in series with armature during starting period.
High current would likely cause severe damage to brushes, commutator, or windings.

45
Q

List the four nameplate ratings for a DC motor.

A

Voltage, Current, Power, Speed

46
Q

Electrochemistry

A

When combined with certain metals, certain chemicals cause a chemical reaction that will transfer electrons to produce electrical energy

47
Q

Chemical Cell

A

Composed of two electrodes made of different types of metal or metallic compounds immersed in an electrolyte solution.

48
Q

Batteries

A

Consists of two or more chemical cells connected in series. The combination of materials converts chemical energy into electrical energy

49
Q

Static Electricity

A

• Neutral state (atoms with zero charge) –proper number of electrons in orbit around atoms; will neither attract nor repel other matter in its vicinity
• If electrons are removed from the atoms, they become electrically positive
– For example, friction when a glass rod is rubbed with a silk cloth
• If this body of matter (e.g. glass rod) comes near, but not in contact with, another body having a normal charge
– an electric force is exerted between them because of their unequal charges

50
Q

Magnetic Induction

A

Generator – machine that converts mechanical energy into electrical energy using the principle of magnetic induction

51
Q

DC Generator

A

Consists of an armature coil with a single turn of wire

52
Q

Thermoelectricity

A

Some materials readily give up their electrons and others readily accept electrons
When two dissimilar metals like copper and zinc are joined together
Transfer of electrons take place
Electrons leave the copper atoms and enter the zinc atoms
This creates a voltage potential across the junction of the two metals
When heat energy is applied to the junction, more electrons are released, and the voltage potential becomes greater
When heat is removed and the junction cools, the charges will dissipate and the voltage potential will decrease
A thermocouple is an example of a device that relies on thermoelectricity to produce a voltage

53
Q

Piezoelectric Effect

A

An example is the crystal phonograph cartridge that contains a Rochelle salt crystal
A phonograph needle is attached to the crystal
As the needle moves in the grooves of a record, it swings from side to side, applying compression and decompression to the crystal
This mechanical motion applied to the crystal generates a voltage signal that is used to reproduce sound

54
Q

State the purpose of a rectifier and describe the outputs of rectifier circuits.

A

The purpose of a rectifier circuit is to convert AC power to DC.

Foundations (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions