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Engineering > Unit 4 - Electronics > Flashcards

Unit 4 - Electronics Flashcards

1
Q

Outline the equation for resistance in series

A

R1 + R2 + R3 = RT

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2
Q

Outline the equation for resistance in parallel

A

1/R1 + 1/R2 + 1/R3 = 1/RT

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3
Q

Outline Ohm’s law

A

V=IR

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4
Q

Outline the equation for charge and potential energy in terms of power and time

A

W = Pt
charge = power x time

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5
Q

Outline the 3 equations for power in terms of current, voltage and resistance

A

P = IV
P = I^2 x R
P = v^2 / R

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6
Q

Outline the equation for voltage out of a voltage divider

A

(Vin x R2) / (R1 + R2) = Vout

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7
Q

Outline Kirchhoff’s current law

A

sum of the current entering a node must equal the sum of the current exiting the node

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8
Q

Outline Kirchhoff’s voltage law

A

sum of voltage loss over components must be equal to the total voltage supplied

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9
Q

Outline an AND gate and it’s outputs

A

=|)-
A B Q
0 0 0
0 1 0
1 0 0
1 1 1

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10
Q

Outline a NAND gate and it’s outputs

A

=|)0-
A B Q
0 0 1
0 1 1
1 0 1
1 1 0

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11
Q

Outline an OR gate and it’s outputs

A

=)>-
A B Q
0 0 0
0 1 1
1 0 1
1 1 1

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12
Q

Outline a NOR gate and it’s outputs

A

=)>0-
A B Q
0 0 1
0 1 0
1 0 0
1 1 0

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13
Q

Outline a XOR/EOR gate and it’s outputs

A

=))>-
A B Q
0 0 0
0 1 1
1 0 1
1 1 0

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14
Q

Outline a XNOR/ENOR gate and it’s outputs

A

=))>0-
A B Q
0 0 1
0 1 0
1 0 0
1 1 1

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15
Q

Outline a NOT gate and it’s outputs

A
  • |>0-
    A Q
    0 1
    1 0
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16
Q

Outline the purpose of a ‘+’ in boolean logic

A

OR gate

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17
Q

Outline the purpose of a ‘.’ in boolean logic

A

AND gate

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18
Q

Outline the purpose of a ‘-‘ on top of inputs in boolean logic

A

NOT gate

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19
Q

Outline De Morgan’s theorem

A

(A.B) bar = A bar + B bar
(A+B) bar = A bar . B bar

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20
Q

Outline the characteristics of an ideal operational amplifier

A
  • infinite open-loop gain
  • infinite input resistance
  • infinite bandwidth
  • zero output resistance
  • output of zero when inputs are identical
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21
Q

Outline the equation for gain in an operation amplifier

A

Vout / Vin

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22
Q

Outline the equation for gain in a non-inverting amplifier

A

1 + Rf/Rd

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23
Q

Outline the equation for gain in an inverting amplifier

A

-Rf/Rin

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24
Q

Outline the equation for gain in a summing amplifier

A

-Rf(V1/R1 + V2/R2 + V3/R3)

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25
Q

Outline the term DC Power

A

direct current
current flows in one direction at a constant rate

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26
Q

Outline the term AC Power

A

alternating current
current continually changes direction, fluctuating along a frequency in the form of a sine wave

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27
Q

Outline the voltage outputs of points on the national grid

A

Extra high voltage (EHV):
Power stations - 400 000V
Grid supply points (GSPs) - 132 000V
Bulk Supply points - 33 000 V

High voltage (HV):
Substations - 11 000 V

Low voltage (LV):
distribution transformers - 240 V

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28
Q

Outline the total electrical energy used in the UK

A

1.3EJ (1.3 x 10^18 Joules)

29
Q

Outline the equation for Electrical energy

A

E = Pt

30
Q

Outline the equation for Vrms for single phase power

A

Vpeak / root 2

31
Q

Outline the equation for power for three phase power

A

1/3 [(V1-V2)^2 + (V2-V3)^2 + (V1-V3)^2]

32
Q

Outline the benefits of using single phase power

A
  • simpler and therefore cheaper to construct
  • more efficient at low powers
33
Q

Outline the benefits of using three phase power

A
  • constant power (no fluctuations)
  • multiple voltages available
  • thinner and therefore cheaper cables can be used due to being constant
34
Q

Outline the voltage for single phase power

A

240V

35
Q

Outline the voltage for three phase power

A

415V

36
Q

Outline the stages of AC to DC rectification

A
  • AC input
  • Transformer
  • Rectifier
  • Smoothing circuit
  • Stabilising circuit
  • DC output
37
Q

Outline the transformer stage of AC to DC rectification

A

Lowing the voltage and current enough to be safe for people and circuits

38
Q

Outline the rectifier stage of AC to DC rectification

A

uses diodes to ensure a purely positive voltage (could flip the voltage when negative or could delete the negative voltage)

using a diode results in 0.7V loss in every use - bridge rectifiers lose 1.4V as they use 2 diodes

39
Q

Outline the Smoothing circuit stage of AC to DC rectification

A

uses a capacitor to even out the fluctuations (does not fully flatten)

capacitor maintains voltage for a short period of time before slowly dissipating. Whilst dissipating, the voltage jumps up again, resupplying the capacitor (bumpy wave)

40
Q

Outline the Stabilising stage of AC to DC rectification

A

uses a Zener diode in reverse to completely flatten the signal

loses 0.7V

Transforms all voltage above a set value into thermal energy - important to smooth the wave as much as possible in Smoothing circuit phase to minimise this

41
Q

Outline the safety features used in AC to DC rectification

A

Fuse - blows if there is too much current - stops device from braking

Diode - prevents current going the wrong way

Resistor - stops the components blowing

42
Q

Outline the equation for Vrms using a sign wave

A

Vpeak x sin(2 x pi x frequency x time)

for Vpeak is the peak on a sine graph and time is the x-axis

43
Q

Outline the equation for w (omega) in a sign graph

A

2 x pi x frequency

44
Q

Outline the equation linking frequency and a time period

A

1/T = f
1/f = T
fT = 1

45
Q

Outline the purpose of resistors

A

Resistors convert energy to heat, in a process known as joule/ohmic/resistive heating
represented by the letter R

46
Q

Outline the purpose of capacitors

A

resist continuous current
temporarily store electrical energy in an electric field between two parallel plates

represented by the letter C

47
Q

Outline the purpose of inductors

A

resist changing current
temporarily stores electrical energy in a magnetic field
induces a magnetic field

represented by the letter L

48
Q

Outline reactance

A

the resistance to the flow of current
sum resistance

represented by the letter X

49
Q

Outline the equation for reactance in an RL circuit

A

XL = 2piFL

for F is frequency and L is inductance

50
Q

Outline the equation for reactance in an RC circuit

A

XC = 1 / 2piFC

for F is frequency and C is capacitance

51
Q

Outline impedance

A

When circuit element converts electrical energy to another form

represented by the letter Z

52
Q

Outline the equation for impedance in an RL circuit

A

Z = root (R2 + XL2)

for R is the resistance and XL is the inductor reactance

53
Q

Outline the equation for impedance in an RC circuit

A

Z = root (R2 + XC2)

for R is the resistance and XC is the capacitor reactance

54
Q

Outline what is meant by phase shift

A

because inductors oppose a change in current and capacitors oppose a continuous current, there is a lag between the graphs for current and voltage

55
Q

Outline phase shift in inductors

A

voltage: sin(x)
current: sin(x-theta)

current is shifted along the x axis by a positive theta (phase angle)

56
Q

Outline phase shift in capacitors

A

voltage: sin(x)
current: sin(x+theta)

current is shifted along the x axis by a negative theta (phase angle)

57
Q

Outline what is meant by the phase angle

A

the angle at which the current has been shifted along from the voltage (phase shift)

58
Q

Outline the equation for the phase angle

A

theta = arccos (R / Z)

for R is resistance and Z is impedance

59
Q

Outline the cause of voltage lead

A

Inductors

60
Q

Outline the cause of voltage lag

A

Capacitors

61
Q

Outline the equation for impedance in an RLC circuit

A

z = root (R2 + (XL - XC)2)

for R is resistance, XL is inductor reactance and XC is capacitor reactance

62
Q

Outline what happens to the voltage lead and voltage lag in an RLC circuit

A

the lag caused by the capacitor and the lead caused by the inductor are equal and therefore cancel out

there is no overall voltage lead or lag

63
Q

Outline what is meant by the Power Factor in an RLC circuit

A

how much power is being used in the resistor of the circuit

64
Q

Outline the equation for Power Factor in an RLC circuit

A

R / Z
cos phi

for R is resistance, Z is impedance and phi is the phase angle

65
Q

Outline how to achieve an optimal Power Factor in an RLC circuit

A

R = Z therefore XC = XL

for r is resistance, z is impedance, XC is capacitor reactance and XL is inductor reactance

The Power Factor will be equal to 1

66
Q

Outline the restraints of Power Factor in an RLC circuit

A

If R < Z then PF will be between 1 and 0

If R = Z then PF will be 1

R cannot be greater than Z

67
Q

Outline a phasor diagram with no resistance

A

the arrow will be perfectly zertical

68
Q

Outline a phasor diagram with no reactance

A

the arrow will be perfectly horizontal

69
Q

Outline what is indicated by an up and down arrow in a phasor diagram

A

up - voltage lead (inductor)

down - voltage lag (capacitor)

Engineering (3 decks)

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