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Electrical Theory 1 > General Knowledge > Flashcards

General Knowledge Flashcards

1
Q

What holds the electron in orbit around the nucleus?

A

A force of attraction

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2
Q

Potential difference will exist between two points in the circuit that have a?

A

Difference in charge

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3
Q

to produce a Voltage chemically, the two metals need to be made of?

A

Dissimilar metals

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4
Q

Name 3 requirements needed to produce voltage by induction

A

1: Electrical conductor
2: Magnetic field
3: Relative movement

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5
Q

What are the lines of force that pass through a space surrounding a magnet called?

A

Lines of magnetic flux

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6
Q

3 materials that mixed with steel, will produce stronger magnets

A

Aluminium
Cobalt
Nickel

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7
Q

What is produced around a conductor when a current is passed through it?

A

Lines of magnetic flux

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8
Q

There are 3 requirements needed for magnetism to produce voltage by induction, they are?

A

Conductor
Magnetic field
Relative movement

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9
Q

What direction does AC travel through a conductor?

A

Both ways ( it alternates)

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10
Q

List 2 advantages of AC over DC

A

Wiring & equipment can be lighter.

Easier to transform

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11
Q

The level to which the voltage or current rises to is called?

A

Amplitude

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12
Q

How are AC cycles per second expressed?

A

Hertz

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13
Q

What are the values of the ships main electrical supplies?

A

3 Phase
450 V
60 Hertz

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14
Q

What is the frequency equation?

A

Time (Seconds) = I divided Frequency

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15
Q

List 4 advantages of an AC motor

A
  1. Less maintenance
  2. More efficient
  3. Cheaper
  4. More compact
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16
Q

What is the main disadvantage of AC?

A

It’s difficult to vary speed

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17
Q

List the 2 main components of an AC motor

A
  • Stator
  • Rotor
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18
Q

What causes movement in a 3 phase induction motor?

A

The rotating magnetic field generated by the stator

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19
Q

What is the most common AC motor used in the navy?

A

Squirrel Cage

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20
Q

List the components of a Squirrel cage

A
  1. Non drive end bearing
  2. Copper end ring
  3. Copper bars
  4. Drive end bearing
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21
Q

How does the rotating magnetic field from the stator cause the rotor to rotate?

A
  1. The rotating field induces a current
  2. The current causes a magnetic field
  3. The interaction between the two magnetic fields causes the rotor to ‘follow’ the rotating field.
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22
Q

What will happen if a running 3 phase AC motor were to lose 1 phase of input?

A
  • Keep running
  • Lose power
  • Vibrate
  • Create excessive noise
  • Heat up
23
Q

What is Back EMF?

A

It is opposite in polarity to the EMF that is being applied to the conductor

24
Q

What position must the carbon brushes be fixed and why?

A
  • MNA (Magnetic neutral axis)
  • To stop sparking of the brushes
25
Q

What are Inter-Poles and what do they do?

A
  • They assist in giving sparkless commutation, by neutralising the effect of armature reaction.
  • They are poles similar to the main poles but smaller
26
Q

What is the name given to materials in a solar panel?

A

Semiconductors

27
Q

What’s the difference between Volts, Watts And Current?

A
  • Voltage (Volts) is like water pressure in a pipe, i.e. How hard is the electricity pushing?
  • Current (Amps) is like the volume of water flowing in a pipe i.e. How much water is flowing?
  • Power (Watts) is the product of the two, when you multiply Voltage by Current you get Power.
28
Q

What is Torque?

A

a force that tends to cause rotation.

29
Q

What is an armature?

A

a device through which electric current is passed for generating torque (rotor).

30
Q

What is magnetic flux?

A

Magnetic flux is a measurement of the total magnetic field which passes through a given area

31
Q

What is the Magnetic Neutral Axis (MNA)?

A

The axis on which there is no Flux generated in the armature conductors. Because they move parallel to the main field flux lines.

32
Q

What is Field winding?

A

Where the main field flux is produced

33
Q

What are interpoles?

A

Interpoles are designed in DC motors To counter act armature reaction, they are smaller than the main poles

34
Q

What is Lamination for?

A

to improve efficiency of transformer

35
Q

What is torque?

A

Rotational forces

36
Q

Name the 3 classifications of DC motors.

A
  1. Series
  2. Shunt
  3. Compound
37
Q

What is a secondary cell?

A

An electric cell that can be recharged and can be used to store chemical energy

38
Q

What is an electrolyte?

A

A liquid that can conduct electricity using a chemical reaction

39
Q

What is the difference between magnetic flux and magnetic field?

A
  • Magnetic field describes a region where a magnetic force can be felt.
  • Magnetic flux describes how much magnetic field passes through an area
40
Q

What is an advantage of DC over AC?

A

Better speed control

41
Q

The amount of torque produced by a motor depends on?

A
  • Strength of magnetic field
  • Size of the armature current
42
Q

Define power?

A

The rate of doing work

43
Q

Electric power depends on?

A
  1. The number of electrons to be moved
  2. The speed in which the are made to travel
44
Q

1 horsepower =?

A

746 watts

45
Q

Earth faults can be caused by?

A
  • Dampness
  • Old, brittle insulation
  • Accidental damage
46
Q

A transformer consists of 2 coils close together but insulated from one another. What are they called?

A

Primary and secondary windings

47
Q

What is the equation for transformers?

A

Output V= No. secondary turns / No. primary turns x input V

48
Q

What is the purpose of a HF (High frequency) Generator?

A

To give voltage to the AVR

49
Q

The 3 sets of windings of a 3-phase motor are usually connected in 2 which ways?

A
  1. Star
  2. Delta
50
Q

Describe the Compound wound motor.

A

A combination of series and shunt.

Has the best of both motors.

51
Q

Name the 2 neutral axis associated with DC motors

A
  • Geometric neutral axis
  • Magnetic neutral axis
52
Q

what is another term for Commutator?

A

Split ring

53
Q

What is the difference between Split ring & Slip ring?

A

The slip ring is a closed circle (used in AC motors)

The Split ring is divided (used in DC motors)

54
Q

Why wont DC current work with transformers?

A

because there is no change in the magnetic field

Electrical Theory 1 (14 decks)

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