Unit 4 - Electronics Flashcards
Outline the equation for resistance in series
R1 + R2 + R3 = RT
Outline the equation for resistance in parallel
1/R1 + 1/R2 + 1/R3 = 1/RT
Outline Ohm’s law
V=IR
Outline the equation for charge and potential energy in terms of power and time
W = Pt
charge = power x time
Outline the 3 equations for power in terms of current, voltage and resistance
P = IV
P = I^2 x R
P = v^2 / R
Outline the equation for voltage out of a voltage divider
(Vin x R2) / (R1 + R2) = Vout
Outline Kirchhoff’s current law
sum of the current entering a node must equal the sum of the current exiting the node
Outline Kirchhoff’s voltage law
sum of voltage loss over components must be equal to the total voltage supplied
Outline an AND gate and it’s outputs
=|)-
A B Q
0 0 0
0 1 0
1 0 0
1 1 1
Outline a NAND gate and it’s outputs
=|)0-
A B Q
0 0 1
0 1 1
1 0 1
1 1 0
Outline an OR gate and it’s outputs
=)>-
A B Q
0 0 0
0 1 1
1 0 1
1 1 1
Outline a NOR gate and it’s outputs
=)>0-
A B Q
0 0 1
0 1 0
1 0 0
1 1 0
Outline a XOR/EOR gate and it’s outputs
=))>-
A B Q
0 0 0
0 1 1
1 0 1
1 1 0
Outline a XNOR/ENOR gate and it’s outputs
=))>0-
A B Q
0 0 1
0 1 0
1 0 0
1 1 1
Outline a NOT gate and it’s outputs
- |>0-
A Q
0 1
1 0
Outline the purpose of a ‘+’ in boolean logic
OR gate
Outline the purpose of a ‘.’ in boolean logic
AND gate
Outline the purpose of a ‘-‘ on top of inputs in boolean logic
NOT gate
Outline De Morgan’s theorem
(A.B) bar = A bar + B bar
(A+B) bar = A bar . B bar
Outline the characteristics of an ideal operational amplifier
- infinite open-loop gain
- infinite input resistance
- infinite bandwidth
- zero output resistance
- output of zero when inputs are identical
Outline the equation for gain in an operation amplifier
Vout / Vin
Outline the equation for gain in a non-inverting amplifier
1 + Rf/Rd
Outline the equation for gain in an inverting amplifier
-Rf/Rin
Outline the equation for gain in a summing amplifier
-Rf(V1/R1 + V2/R2 + V3/R3)
Outline the term DC Power
direct current
current flows in one direction at a constant rate
Outline the term AC Power
alternating current
current continually changes direction, fluctuating along a frequency in the form of a sine wave
Outline the voltage outputs of points on the national grid
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
Outline the total electrical energy used in the UK
1.3EJ (1.3 x 10^18 Joules)
Outline the equation for Electrical energy
E = Pt
Outline the equation for Vrms for single phase power
Vpeak / root 2
Outline the equation for power for three phase power
1/3 [(V1-V2)^2 + (V2-V3)^2 + (V1-V3)^2]
Outline the benefits of using single phase power
- simpler and therefore cheaper to construct
- more efficient at low powers
Outline the benefits of using three phase power
- constant power (no fluctuations)
- multiple voltages available
- thinner and therefore cheaper cables can be used due to being constant
Outline the voltage for single phase power
240V
Outline the voltage for three phase power
415V
Outline the stages of AC to DC rectification
- AC input
- Transformer
- Rectifier
- Smoothing circuit
- Stabilising circuit
- DC output
Outline the transformer stage of AC to DC rectification
Lowing the voltage and current enough to be safe for people and circuits
Outline the rectifier stage of AC to DC rectification
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
Outline the Smoothing circuit stage of AC to DC rectification
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)
Outline the Stabilising stage of AC to DC rectification
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
Outline the safety features used in AC to DC rectification
Fuse - blows if there is too much current - stops device from braking
Diode - prevents current going the wrong way
Resistor - stops the components blowing
Outline the equation for Vrms using a sign wave
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
Outline the equation for w (omega) in a sign graph
2 x pi x frequency
Outline the equation linking frequency and a time period
1/T = f
1/f = T
fT = 1
Outline the purpose of resistors
Resistors convert energy to heat, in a process known as joule/ohmic/resistive heating
represented by the letter R
Outline the purpose of capacitors
resist continuous current
temporarily store electrical energy in an electric field between two parallel plates
represented by the letter C
Outline the purpose of inductors
resist changing current
temporarily stores electrical energy in a magnetic field
induces a magnetic field
represented by the letter L
Outline reactance
the resistance to the flow of current
sum resistance
represented by the letter X
Outline the equation for reactance in an RL circuit
XL = 2piFL
for F is frequency and L is inductance
Outline the equation for reactance in an RC circuit
XC = 1 / 2piFC
for F is frequency and C is capacitance
Outline impedance
When circuit element converts electrical energy to another form
represented by the letter Z
Outline the equation for impedance in an RL circuit
Z = root (R2 + XL2)
for R is the resistance and XL is the inductor reactance
Outline the equation for impedance in an RC circuit
Z = root (R2 + XC2)
for R is the resistance and XC is the capacitor reactance
Outline what is meant by phase shift
because inductors oppose a change in current and capacitors oppose a continuous current, there is a lag between the graphs for current and voltage
Outline phase shift in inductors
voltage: sin(x)
current: sin(x-theta)
current is shifted along the x axis by a positive theta (phase angle)
Outline phase shift in capacitors
voltage: sin(x)
current: sin(x+theta)
current is shifted along the x axis by a negative theta (phase angle)
Outline what is meant by the phase angle
the angle at which the current has been shifted along from the voltage (phase shift)
Outline the equation for the phase angle
theta = arccos (R / Z)
for R is resistance and Z is impedance
Outline the cause of voltage lead
Inductors
Outline the cause of voltage lag
Capacitors
Outline the equation for impedance in an RLC circuit
z = root (R2 + (XL - XC)2)
for R is resistance, XL is inductor reactance and XC is capacitor reactance
Outline what happens to the voltage lead and voltage lag in an RLC circuit
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
Outline what is meant by the Power Factor in an RLC circuit
how much power is being used in the resistor of the circuit
Outline the equation for Power Factor in an RLC circuit
R / Z
cos phi
for R is resistance, Z is impedance and phi is the phase angle
Outline how to achieve an optimal Power Factor in an RLC circuit
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
Outline the restraints of Power Factor in an RLC circuit
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
Outline a phasor diagram with no resistance
the arrow will be perfectly zertical
Outline a phasor diagram with no reactance
the arrow will be perfectly horizontal
Outline what is indicated by an up and down arrow in a phasor diagram
up - voltage lead (inductor)
down - voltage lag (capacitor)
