Electronics Flashcards
(127 cards)
1
Q
What are the four parts of a basic electrical system?
A
- The source
- The load
- The transmission system
- The control apparatus
The source provides energy, the load absorbs energy, the transmission system conducts energy, and the control apparatus manages the flow of energy.
2
Q
What is the SI unit of Electric Charge?
A
Coulomb (C)
One coulomb is the charge carried by approximately 6.21 x 10^18 electrons.
3
Q
What is the charge of a single electron?
A
1.6 x 10^-19 C
This is a fundamental constant in electrostatics.
4
Q
What is a conductor?
A
A material that allows current to flow freely
Common examples include Copper and Aluminium.
5
Q
What characterizes an insulator?
A
Limited free electrons
Examples include materials like plastics.
6
Q
What does the electric field represent?
A
A region where an electric charge experiences a force
The direction of the field is toward which a positive charge would move.
7
Q
What is conventional current?
A
The flow of positive charge in a circuit
It is defined as the amount of charge passing through a cross-section per second.
8
Q
What is the unit of current?
A
Ampere (A)
A current of 1 A flows when 1 coulomb of charge crosses a point in 1 second.
9
Q
What is voltage?
A
The potential difference between two points
Voltage is synonymous with potential difference.
10
Q
What is the unit of potential difference?
A
Volt (V)
One volt is the potential difference that allows one joule of energy to move one coulomb of charge.
11
Q
What is the relationship defined by Ohm’s Law?
A
V = IR
This means voltage (V) is equal to the product of current (I) and resistance (R).
12
Q
What does resistance measure?
A
Opposition to the electrical current flow
The unit of resistance is Ohm (Ω).
13
Q
What is Power in an electrical context?
A
The rate at which energy is converted from one form to another
Power can be calculated using P = VI, where P is power, V is voltage, and I is current.
14
Q
What happens to resistance as the temperature of a conductor increases?
A
Resistance increases
However, at very low temperatures, some materials can become superconductors with zero resistance.
15
Q
What is Kirchhoff’s Current Law (KCL)?
A
The algebraic sum of currents at a junction must equal zero
This means that the total current flowing into a node equals the total current flowing out.
16
Q
What is Kirchhoff’s Voltage Law (KVL)?
A
The sum of the electrical potential differences around any closed circuit is zero
This law is fundamental for circuit analysis.
17
Q
What does the term ‘electromotive force’ (EMF) represent?
A
The energy expended per unit charge as it moves through a source
The unit of EMF is also Volt (V).
18
Q
How is voltage measured in a circuit?
A
With a voltmeter
Voltmeters are always placed in parallel to the component being measured.
19
Q
Fill in the blank: The voltage across a resistor is proportional to the _______ that flows through it.
A
current
This is a restatement of Ohm’s Law.
20
Q
What is the formula for calculating power in an electrical circuit?
A
P = VI
Where P is power, V is voltage, and I is current.
21
Q
True or False: The resistance of a wire decreases as its length increases.
A
False
Longer wires have more resistance.
22
Q
What are the characteristics of electric charge?
A
- Charge can be positive or negative
- Carriers of negative charge are electrons
- Carriers of positive charge are protons
A deficit of electrons results in a net positive charge and a surplus results in a net negative charge.
23
Q
What does Kirchhoff’s Current Law (KCL) state?
A
The currents flowing into a node are equal to the currents flowing out of that node.
KCL is an essential principle in electrical engineering for analyzing current flow in circuits.
24
Q
In KCL, how are positive and negative signs allocated to currents?
A
Positive signs are allocated to currents entering the node; negative signs are allocated to those leaving the node.
25
What is the algebraic sum of currents in KCL?
The algebraic sum of currents entering a node equals the algebraic sum of currents leaving that node.
26
What is Kirchhoff’s Voltage Law (KVL)?
In any closed loop within a network, the algebraic sum of the voltage drops plus the algebraic sum of the electromotive forces (E.M.Fs) equals zero.
27
What is the significance of voltage polarity in KVL?
A rise in voltage is indicated with a positive sign, while a fall in voltage is indicated with a negative sign.
28
What happens to voltage when moving from a battery's negative terminal to its positive terminal?
There is a potential increase.
29
What happens to voltage when moving from a battery's positive terminal to its negative terminal?
There is a potential decrease.
30
In KVL, what is the relationship between voltage rises and voltage drops?
The total voltage rises must equal the total voltage drops in a closed path of a circuit.
31
What is the formula for voltage division in a series circuit?
V1/V = R1/(R1+R2) and V2/V = R2/(R1+R2).
32
What characterizes a series circuit?
Conductors with resistances are linked end-to-end, providing a single path for current to flow.
33
What characterizes a parallel circuit?
Conductors with resistances are connected across each other, allowing multiple paths for current to flow.
34
How is the total voltage in a series circuit calculated?
The total voltage equals the sum of the voltages across the different parts of the circuit.
35
What is Ohm's Law?
V = I * R, where V is voltage, I is current, and R is resistance.
36
What is the effective resistance in a series circuit?
The effective resistance is the sum of the individual resistances: R = R1 + R2 + R3.
37
What is the current relationship in a parallel circuit?
The total current supplied to the network equals the sum of currents in various branches.
38
What is the equivalent resistance in a parallel circuit?
The effective (equivalent) resistance is always smaller than the smallest resistor in the circuit.
39
How is voltage across resistors in a parallel circuit characterized?
The voltage drop across each branch is equal to the supply voltage applied to the network.
40
Fill in the blank: The algebraic sum of all voltages around any closed loop in a circuit equals _______.
zero.
41
True or False: In KVL, the net effect of all energy sources and energy losses within the circuit equals zero when you complete a loop.
True.
42
How do you calculate the total current in a parallel circuit?
I = I1 + I2 + I3.
43
Calculate the effective resistance of two resistors in parallel, R1 = 14Ω and R2 = 28Ω.
RT = 9.3Ω.
44
What is the relationship between voltage and current in a series circuit?
The relationship between V and I keeps the same across all components.
45
What is the voltage division rule used for?
To determine the division of volt drops in a simple series circuit.
46
What is the formula to calculate effective resistance in a series circuit?
R = R1 + R2 + R3
## Footnote
This formula states that the effective resistance in a series circuit is the sum of all individual resistances.
47
How do you calculate supply current using voltage and resistance?
I = V / R
## Footnote
This formula is derived from Ohm's law, where I is the current, V is the voltage, and R is the resistance.
48
What is the output voltage of a voltage divider with an input voltage of 30V and R2 = 100Ω if the desired output is 10V?
Calculate R1 using the voltage divider formula.
## Footnote
The voltage divider formula is Vout = Vin * (R2 / (R1 + R2)).
49
What is the threshold voltage (Vth) for silicon and germanium diodes to conduct current?
Silicon: 0.7V, Germanium: 0.3V
## Footnote
This threshold voltage is necessary for the diode to enter the forward bias region.
50
What is a PN junction?
A junction formed when a p-type semiconductor contacts an n-type semiconductor
## Footnote
The PN junction is fundamental in the operation of diodes and transistors.
51
What happens when a diode is reverse biased?
The depletion zone widens, preventing current flow
## Footnote
In reverse bias, the diode acts as an insulator.
52
What is the difference between majority and minority carriers in semiconductors?
Majority carriers are the dominant charge carriers; minority carriers are the less abundant ones.
## Footnote
In N-type silicon, majority carriers are electrons and in P-type silicon, majority carriers are holes.
53
What is the average value of the half-wave rectified voltage if Vm = 50V?
Vavg = Vm / π = 50 / π = 15.9V
## Footnote
This calculation shows how to determine the average output voltage from a half-wave rectifier.
54
What is the main function of Zener diodes?
To act as voltage regulators and provide a stable reference voltage
## Footnote
Zener diodes can conduct in reverse-biased mode, allowing them to maintain a constant voltage.
55
Fill in the blank: A diode allows current to flow in ______ direction only.
one
## Footnote
This characteristic makes diodes essential for controlling current direction in circuits.
56
What type of current flows through a diode in reverse bias?
A small leakage current flows due to minority charge carriers
## Footnote
This current is typically very small and does not significantly affect the circuit.
57
What is the formula for the average load current in a bridge rectifier circuit?
Idc = Vdc / R
## Footnote
The average load current can be calculated by dividing the DC voltage by the resistive load.
58
What occurs in the forward bias region of a diode?
Current flows from the P-type to the N-type material
## Footnote
This happens when a positive voltage is applied to the P-side and negative to the N-side.
59
What is an ideal diode's behavior in the forward bias region?
No threshold voltage, zero resistance, instantaneous current flow
## Footnote
Ideal diodes are theoretical devices that simplify circuit analysis.
60
What is a half-wave rectifier?
A circuit that allows only one half of the AC waveform to pass, producing pulsating DC
## Footnote
It uses a single diode to achieve this rectification.
61
True or False: A full-wave rectifier converts both positive and negative halves of the AC waveform.
True
## Footnote
This allows for a more efficient conversion of AC to DC compared to half-wave rectifiers.
62
What is the breakdown voltage in a diode?
The reverse voltage at which the diode conducts a large current in the reverse direction
## Footnote
Special types of diodes, like Zener diodes, are designed to operate in this region.
63
What is the role of doping in semiconductors?
To increase the number of charge carriers (electrons or holes) in the material
## Footnote
Doping changes the electrical properties of intrinsic semiconductors.
64
What is the effect of doping silicon with phosphorus?
Creates N-type silicon with excess free electrons
## Footnote
Phosphorus has 5 valence electrons, providing additional charge carriers.
65
What is the effect of doping silicon with boron?
Creates P-type silicon with holes as majority carriers
## Footnote
Boron has 3 valence electrons, resulting in a deficiency of electrons.
66
What are photodiodes used for?
Optical communication
## Footnote
Photodiodes are semiconductor devices that convert light into electrical current.
67
What is a Zener diode?
A special diode also known as voltage regulator diodes
## Footnote
Used widely as voltage reference sources in electronics circuitry.
68
What is the primary function of a rectifier circuit?
To convert alternating current to direct current.
69
What is the difference between half-wave and full-wave rectification?
Half-wave rectification uses a single diode; full-wave rectification requires at least two diodes.
70
What is smoothing in the context of rectifiers?
The process of removing the worst of the output variations in the current.
71
What are the three terminals of a Bipolar Junction Transistor (BJT)?
Base (B), Collector (C), Emitter (E).
72
What does the term 'bipolar' refer to in BJTs?
The use of both holes and electrons as current carriers.
73
What are the two main types of BJTs?
NPN and PNP.
74
What is the typical current gain (β) range for BJTs?
Between 20 and 200.
75
What is the purpose of biasing in BJTs?
To ensure proper operation as an amplifier.
76
What happens during the forward bias of a BJT?
Holes jump over the barrier into the N region as minority carriers.
77
What is the cutoff region for a BJT?
When the transistor is effectively turned off, and no current flows.
78
What is the saturation region for a BJT?
Both the BE and BC junctions are forward-biased, allowing maximum current flow.
79
What is the active region in a BJT?
The base-emitter junction is forward-biased, while the base-collector junction is reverse-biased.
80
What is the Q-point in a transistor circuit?
The point at which the transistor operates in the active region for amplification.
81
What is an operational amplifier (Op-amp)?
A high-gain electronic voltage amplifier with differential input and usually a single-ended output.
82
What are the ideal characteristics of an Op-amp?
* Infinite input impedance
* Infinite gain for differential input
* Zero output impedance
83
What distinguishes open-loop mode from closed-loop mode in Op-amps?
Open-loop has very high gain; closed-loop applies feedback for stability and control.
84
What is the function of feedback in Op-amps?
Increases stability and linearity.
85
What is the role of a rectifier in a power supply?
To convert AC voltage to a steady DC voltage.
86
What is the significance of the barrier potential in a PN junction?
It prevents the flow of charge carriers across the junction.
87
What is the purpose of smoothing capacitors in rectifier circuits?
To reduce ripple voltage in the output.
88
Fill in the blank: A transistor is used to ______ electronic signals.
[amplify or switch]
89
What happens to the collector current (IC) in saturation mode of a BJT?
IC is independent of IB.
90
What is the open-loop mode of an op-amp?
Very high gain used in comparator circuits
## Footnote
In open-loop mode, the output is driven to saturation.
91
What is the role of feedback in closed-loop mode for op-amps?
Increases stability and linearity; gain determined by external components
## Footnote
Feedback is essential for controlling the gain in closed-loop configurations.
92
What happens when v+ > v- in an open-loop op-amp?
The amplifier is driven into saturation, and vo = +V
## Footnote
Conversely, when v+ < v-, vo = -V.
93
What is the primary function of an op-amp?
To amplify the voltage difference between two input voltages (v+ and v-)
## Footnote
This makes it a differential voltage amplifier.
94
Calculate the output voltage of a differential amplifier with an open-loop gain of 120 for input signals 2.45V and 2.35V.
12 V
## Footnote
Calculation: v0 = 120 * (2.45 - 2.35).
95
What applications are comparators used for?
* Square Wave generator
* Zero-crossing detectors
* Voltage level detection
* Data Converters (A/D and D/A converters)
* Oscillators
## Footnote
Comparators output a high or low signal based on input voltage comparisons.
96
What is a zero-crossing detector?
Monitors input voltage and changes output state when input crosses zero volts
## Footnote
Converts a sine wave to a square wave.
97
What are the three possible solutions for non-zero level detection in comparators?
* Battery reference
* Voltage-divider reference
* Zener diode sets reference
## Footnote
These methods allow for setting a reference voltage for comparison.
98
What is the function of negative feedback in op-amps?
Reduces and controls closed-loop voltage gain
## Footnote
Helps the op-amp function as a linear amplifier.
99
Define closed-loop voltage gain (Acl).
Acl = Vout/Vin
## Footnote
It is the voltage gain of an op-amp with external feedback.
100
What is the virtual short circuit rule for voltages in op-amps?
v+ = v-
## Footnote
This is due to the high gain of the op-amp.
101
What does the inverting amplifier configuration do?
Amplifies and inverts the input signal
## Footnote
Feedback is through a resistor connected between output and input.
102
What is the closed-loop gain formula for an inverting amplifier?
Acl = -Rf/Ri
## Footnote
Rf is the feedback resistor and Ri is the input resistor.
103
What is the function of a non-inverting amplifier?
Amplifies the input signal without inverting it
## Footnote
Useful in sensor applications.
104
What is the closed-loop voltage gain formula for a non-inverting amplifier?
Acl = 1 + Rf/Ri
## Footnote
This shows how gain can be adjusted with feedback resistors.
105
What is the purpose of a summing amplifier?
Adds multiple input voltages into a single output
## Footnote
Often used in audio mixers.
106
What is the output voltage formula for a summing amplifier?
Vout = -Rf*(Vin1/R1 + Vin2/R2)
## Footnote
This equation shows how the output is a weighted sum of inputs.
107
What does an op-amp integrator do?
Simulates mathematical integration
## Footnote
Produces an output that is the time integral of the input signal.
108
What is the application of an op-amp differentiator?
Provides the time derivative of the input
## Footnote
Useful for edge detection and motion sensing.
109
What is a latch in digital circuits?
A temporary storage device with two stable states
## Footnote
Used to store a single binary state (0 or 1).
110
What does an SR latch constructed with NOR gates do?
Responds to active-HIGH inputs
## Footnote
Has states for Set, Reset, Hold, and Invalid.
111
What is a flip-flop?
A digital storage device capable of holding a single binary value
## Footnote
The stored value can only be updated at specific moments determined by a clock signal.
112
What is the truth table behavior of a D-type flip-flop?
Q updates to the value of D only on the rising edge of the clock
## Footnote
In the absence of a clock pulse, the output remains unchanged.
113
What controls when the state of the flip-flop is updated?
Clock input
## Footnote
The clock input triggers state changes on flip-flops, typically on signal transitions.
114
When does the Q output update in a D-Type Flip-Flop?
On the rising edge of the clock
## Footnote
In the absence of a clock pulse, the output remains unchanged.
115
What happens to the output of a flip-flop when there is no clock edge?
Hold
## Footnote
The output does not change and maintains its previous state.
116
What is the base of the decimal number system?
10
## Footnote
The decimal system uses digits from 0 to 9.
117
In a decimal number, what does each digit represent?
A multiple of a power of 10
## Footnote
The weights of digits increase from right to left.
118
What is the base of the binary number system?
2
## Footnote
The binary system corresponds to two voltage states: high and low.
119
How can the binary number 1010 be interpreted?
As a decimal number
## Footnote
Each binary digit corresponds to a power of 2.
120
What is the process to convert a binary number to decimal?
Add the decimal equivalents of each position occupied by '1'
## Footnote
Example: 110001 = 32 + 16 + 1 = 49.
121
What method is used to convert a decimal integer to binary?
Division-by-2 method
## Footnote
Repeatedly divide the number by 2 and record the remainders.
122
What is the purpose of an Analogue to Digital converter?
To convert analogue signals into digital binary codes
## Footnote
Involves sampling and holding the analogue signal.
123
What does the sampling process involve in an ADC?
Capturing the amplitude of an analogue signal at specific intervals
## Footnote
The sampled level must be held constant until the next sample.
124
What is the quantization process in ADC?
Mapping sample-and-hold signals to digital numbers
## Footnote
This involves converting voltage levels into binary codes.
125
What is required to create multiple voltage levels in an ADC?
A series of resistors
## Footnote
These levels are then coded with binary numbers.
126
What determines the binary code output in an ADC?
The highest-order input having a HIGH level
## Footnote
Outputs are HIGH when V+ > V- and LOW when V- > V+.
127
What is essential to understand when using fundamental logic gates?
The truth table or functionality
## Footnote
Understanding the operational principles is more important than circuit details.
