Brainscape's Knowledge GenomeTM

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


See full index

AV Fundies > DC Fundamentals 2 > Flashcards

DC Fundamentals 2 Flashcards

1
Q

Describe the construction of a permanent magnet?

A
  • In ferromagnetic materials (Iron, Nickle, and Cobalt), its atoms are grouped into ‘magnetic domains’
  • Each ‘magnetic domain’ acts like its own tiny magnet with a North and South pole
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define the term unmagnetised?

A
  • Domains are arranged randomly
  • The magnetic domains cancel each other out
  • Zero magnetic charge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define the term magnetised?

A
  • An unmagnetised material is under the influence of another magnet
  • The magnetic domains begin to align as the magnet gets closer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define the term fully magnetised?

A
  • The magnetic domains are fully aligned once put under the influence of another magnet
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define the term temporary magnet?

A
  • Becomes a magnet only once its under the influence of another magnet
    E.g. White board in classroom
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define the term permanent magnet?

A
  • Retains its magnetic properties
  • Made from magnetically hard materials, like steel
  • Requires a strong magnetic force to align the magnetic domains
    E.g. White board eraser block
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define the term magnetic axis?

A
  • Imaginary line drawn through the middle of a magnetic field
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define the term magnetic field?

A
  • Force field that surrounds a magnet
  • The distance between the lines represents the strength of the magnetic field
    E.g. Closer the lines - stronger the magnetic field
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define the term magnetising force?

A
  • When a suitable material is placed under the influence of a strong magnetic field
  • Represented by the symbol letter ‘H’
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define the term permeablility?

A
  • Measure of how easy it is for a magnetic force to be established within a material
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define the term retentivity?

A
  • Ability to retain magnetic properties after the magnetising force has been removed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Define the term reluctance?

A
  • How reluctant (resilient) a material is to becoming a magnet
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Define the term saturation?

A
  • The maganetic domains are already aligned so they cannot be used to magnetise - Even with a bigger magnet, there are no available magnetic domains
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Define the term magnetic pole?

A
  • The alignment of the magnetic domains creates points on the magnet where the magnetic field is concentrated
  • North pole and South pole
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Define the term flux density?

A
  • Magnetic field strength is described in terms of ‘flux density’
  • The measure of the number of flux lines per square meter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

2 operating characteristics of a magnet?

A
  • Attraction and repulsion
  • Direction of magnetic lines
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe attraction and repulsion in terms of magnets?

A
  • Opposites attract
    E.g.
  • Pole of magnet 1 connects with similar pole of magnet 2 - they will repel each other
  • Pole of magnet 1 connects with opposing pole of magnet 2 - they will attract each other
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What direction do the magnetic lines travel in:

1) Outside the magnet
2) Inside the magnet

A

Outside: North to South
Inside: South to North

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

Example of a permanent magnet precaution?

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

Define the term keeper?

A
  • Device used to protect a magnet
  • A suitable shaped piece of low reluctance metal, placed between North and South pole magnets
  • Used to protect the magnet
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does a keeper prevent?

A
  • Prevents external magnetic fields from weakening the magnet
  • Prevents the magnet from accidentally influencing magnetically sensitive devices
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the purpose of a magnetic force?

A
  • A magnetic force is used to align the magnetic domains within a material in order to turn it into a magnet
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is Flemming’s left hand rule?

A
  • Grasp conductor in left hand with thumb pointing int he direction of the current flow
  • The fingers wrap around the conductor in the same direction of the lines of the magnetic field
24
Q

Define dart notiation?

A
  • Simple method of indicating the direction of current flow using the cross section of a conductor

Dot: Current is flowing towards you and out of the conductor
Cross: Current is flowing away from you and into the conductor

25
Q

Define the term solenoid?

A
  • A wire which is wound into a series of loops to forma coil, similar to a spring
  • The lines of flux do not cross each other, instead they add together to create a bigger magnetic field
26
Q

How do the magnetic lines of force travel in a solenoid magnetic field?

A
  • Similar to a bar magnet

Outside / Externally: North to South
Inside / Internally: South to North

27
Q

How do you determine magnetic poles in a solenoid?

A
  • Using Flemming’s left hand rule
  • Wrap your fingers in the direction of the current
  • Your thumb will then be pointing the North pole
28
Q

What 2 things is Flemming’s left hand rule used for?

A
  • Determining the direction of current flow
  • Determining the magnetic pole
29
Q

3 factors that affect the strength of a inductor?

A
  • Number of turns the wire that make up the coil
  • Amount of current flow through the coil
  • Distance between adjacent wires in a coil
30
Q

As the strength of a magnetic field increases in a solenoid, what happens to the current flowing through the coil?

A

Strength increases = Current flow increases
(Directly proportional)

31
Q

As the strength of a magnetic field increases in a solenoid, what happens to the number of turns that the wire makes?

A

Strength increases = Number of turns increases
(Directly proportional)

32
Q

As the strength of the magnetic field increases in a solenoid, what happens to the distance between the wires?

A

Strength increases = Distance between the wires decreases
(Inversely proportional)

In other words, the closer together the wires are - the stronger the magnetic field is

33
Q

Describe electromagnetic induction?

A
  • Inducting EMF into something that is not a magnet
  • When current flows through a conductor and a magnetic field is created
34
Q

What happens to the magnetic force when there is no longer relative movement between the lines of flux and the coil of wire?

A
  • Magnetic field will stop
  • EMF will no longer be induced
35
Q

Define Lenz’s law?

A

‘The polarity of the induced EMF is such that any current resulting from it produces magnetic flux that opposes the motion or change producing the EMF’

  • In simple terms, anytime there is a rate of change (movement) in the magnetic lines of force, there is an EMF induced in the solenoid which produces a current which in turn creates magnetic lines of force to oppose the original change
  • The crazy toxic ex law
36
Q

Define Faraday’s law?

A

‘The voltage induced in a conductor by a reaction between the conductor or coil and a magnetic field is directly proportional to the time rate of change of flux linkage s or flux cutting’

37
Q

4 factors affecting the induced EMF in a conductor?

A
  • Magnetic field strength
  • Active length of the conductor
  • Velocity of the cutting effect
  • Angle at which the field is cutting

Induced voltage = Magnetic field x active length x velocity x sin (angle)

38
Q

Describe self induction?

A
  • It does it itself
39
Q

Characteristics of inductors?

A

Symbol: L
Unit: H (Henry’s)
Core types: Iron, air and ferrite

40
Q

3 types of inductor cores?

A
  • Air
  • Iron: Used for high power application
  • Ferrite: Used for low power circuits
41
Q

When will back EMF be at its greatest when powering an inductor circuit?

A
  • The instant that power is applied to the circuit
42
Q

What is self induced voltage with regards to inductors?

A
  • The voltage which is induced into the inductor as a result of a change in current through the conductor
43
Q

Define the term back EMF?

A
  • As circuit current flows, a magnetic field builds in each loop of the inductor which induces EMF in adjacent loops providing an opposing current
44
Q

Factors that affect the self induction of an inductor?

A
  • Linkages
  • Cross sectional area
  • Number of turns
  • Type of core the inductor is wound on
45
Q

Define the term linkages?

A
  • Think of it as ‘How many buddies does he have close by?’
  • A coil with more lays (wound more times) has a much greater inductance
46
Q

Define the term core?

A
  • Refers to the type of centre a coil is wound on
  • High permeability of an iron core would produce less reluctance than an air core
47
Q

Tolerance codes for inductors?

A

M: 20%
K or silver: 10%
J or gold: 5%

48
Q

Applications for back EMF?

A
  • Soft starting
  • Protecting electrical equipment
  • Stabilising the circuit to avoid dips in voltage
49
Q

The time taken for an inductor to reach full charge depends on 2 things, these are?

A
  • Resistance in the circuit
  • Inductance of the inductor

T = L/R

50
Q

2 things to look for in Diodes?

A
  • Is it installed correctly (forward or backwards bias)?
  • Do we have enough voltage?
51
Q

Define diode?

A

‘diode’ is short hand for ‘di-electrode’ with ‘di’ meaning 2

  • PN junction diode is a two-electrode device
52
Q

What does a diode do?

A
  • Only allows current to flow in 1 direction
  • There could be a fault in the circuit but it wont let the current back feed through
  • Protects the circuit
  • Controls the flow
53
Q

How is a serviceability check carried out on a discrete component tester?

A
  • Check the physical condition of the unit, wires and test probes
  • Turn device on to allow the discrete component
    tester to run through its power-on built in test - If no errors are displayed on
    the LCD screen – the serviceability check has passed
54
Q

What are the terms given to the two logic states used in DC circuits?

A
  • Logic 1
  • Logic 0
55
Q

What two conditions must be met for a diode to become forward biased?

A
  • Anode must be connected closer to the positive connection of the
    power supply
  • Cathode must be connected closer to the negative
    connection of the power supply
  • Power supply must be great
    enough to overcome the barrier potential of the diode (0.6V)
56
Q

What are Anode and Cathode, regarding their charge?

A

Anode: positive
Cathode: Negative

57
Q

Define magnetism?

A

The ability of matter to attract other matter to itself

AV Fundies (11 decks)

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