Some Mnemonic phrases for remembering Color Codes of Resistor in Electronics.

Identifying Resistors:

The electronic color code is used to indicate the values or ratings of electronic components, usually for resistors, but also for capacitors, inductors, diodes and others. A separate code, the 25-pair color code, is used to identify wires in some telecommunications cables.

Most axial resistors use a pattern of colored stripes to indicate resistance. SMT ones follow a numerical pattern. Cases are usually brown, blue, or green, though other colors are occasionally found like dark red or dark gray.

Resistor Color Codeing: 

Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White (Gold Silver).

Mnemonic phrases for remembering color codes of resistor:

There are many mnemonic phrases used to remember the order of the colors. They are, but are not limited to, and variations of: 

• Bad Boys Ravish Our Young Girls But Violet Gives Willingly.
• Bad Beer Rots Our Young Guts, But Vodka Goes Well. Get Some Now!  
• B.B. ROY of Great Britain had a Very Good Wife.
• Buffalo Bill Roamed Over Yellow Grass Because Vistas Grand Were God's Sanctuary. 
• Bully Brown Ran Over a Yodeling Goat, Because Violet's Granny Was Gone Snorkeling.
• Buy Better Resistance Or Your Grid Bias May Go Wrong.
• Bill Brown Realized Only Yesterday Good Boys Value Good Work.
• Better Be Ready Or Your Great Big Plan Goes Wrong.
• Better Be Ready Or Your Great Big Venture Goes West.
• Black Bananas Really Offend Your Girlfriend But Violets Get Welcomed.
• Black Birds Run Over Your Biting Visible Gray Worms.
• Big Boys Race Our Young Girls But Violet Generally Wins.
• Black Boys Rape Our Young Girls Behind Victory Garden Walls.
• Black Boys Rape Our Young Girls But Virgins Go Without.

Explanation: 

To remember the color bands on resistors in order of increasing magnitude.

• Numerically the value (0-9) of a resistor via the color-coded bands: Black (0), Brown (1), Red (2), Orange (3), Yellow (4), Green (5), Blue (6), Violet (purple, 7), Gray (8), and White (9).
• Also, note that the red through violet are the colors of the rainbow (in order). Although the ROY G. BIV mnemonic for rainbow colors includes indigo between blue and violet.

Figure 1: A diagram of a resistor, with four color bands A, B, C, D from left to right.

Figure 2: A diagram of a 2.7 Mega Ω color coded resistor. 

To distinguish left from right there is a gap between the C and D bands.

• Band A is the first significant figure of component value (left side)
• Band B is the second significant figure (some precision resistors have a third significant figure, and thus five bands).
• Band C is the decimal multiplier
• Band D if present, indicates tolerance of value in percent (no band means 20%)

For example, a resistor with bands of yellow, violet, red, and gold has first digit 4, second digit 7 (violet), followed by 2 (red) zeros: 4,700 ohms. Gold signifies that the tolerance is ±5%, so the real resistance could lie anywhere between 4,465 and 4,935 ohms.

Figure 3: 4.7 Kilo Ω resistor with ±5% tolerance.

All coded components have at least two value bands and a multiplier; other bands are optional.

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What is a Resistor? What are the Types of Resistors? What are the Applications of Resistor?

What is a Resistor?

A resistor is a passive two-terminal electrical or electronic component that resists an electric current by producing a voltage drop between its terminals in accordance with Ohm's law. The electrical resistance is equal to the voltage drop across the resistor divided by the current through the resistor. 

Figure 1: A typical axial-lead resistor.

Figure 2: Two common schematic symbols of resistor.

In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of electrical power as heat may be used as part of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors have resistances that only change slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements (such as a volume control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical activity.

Theory of Operation:

Ohm's law: The behavior of an ideal resistor is dictated by the relationship specified by Ohm's law:

             V = I/R

Ohm's law states that the voltage (V) across a resistor is proportional to the current (I), where the constant of proportionality is the resistance (R). For example, if a 300 ohm resistor is attached across the terminals of a 12 volt battery, then a current of 12 / 300 = 0.04 amperes flows through that resistor.

Practical resistors also have some inductance and capacitance which affect the relation between voltage and current in alternating current circuits.

The ohm (symbol: Ω) is the SI unit of electrical resistance, named after Georg Simon Ohm. An ohm is equivalent to a volt per ampere. Since resistors are specified and manufactured over a very large range of values, the derived units of milliohm (1 mΩ = 10^-3 Ω), kilohm (1 kΩ = 10³ Ω), and megohm (1 MΩ = 10⁶ Ω) are also in common usage. 

Figure 3: A few types of resistors.

Types of Resistors:

1.     Linear resistors.

                                 i.         Fixed resistors

a)    Led arrangement

b)    Carbon composition

c)     Carbon Pile

d)    Carbon film

e)    Printed carbon resistor

f)      Thick and thin film

g)    Metal film

h)    Metal oxide film

i)      Wire wound

j)      Foil resistor

k)    Ammeter shunt

l)      Grid resistor

m) Special verities

                                    ii.         Variable resistor

a)       Adjustable resistor

b)       Potentiometers

c)        Resistance and decade boxes

d)       Special devices.

2.     Non-linear resistors.

Applications of Resistors:

• In general, a resistor is used to create a known voltage-to-current ratio in an electric circuit. If the current in a circuit is known, then a resistor can be used to create a known potential difference proportional to that current. Conversely, if the potential difference between two points in a circuit is known, a resistor can be used to create a known current proportional to that difference.  
• Current-limiting. By placing a resistor in series with another component, such as a light-emitting diode, the current through that component is reduced to a known safe value.  
• A series resistor can be used for speed regulation of DC motors, such as used on locomotives and train sets.  
• An attenuator is a network of two or more resistors (a voltage divider) used to reduce the voltage of a signal.  
• A line terminator is a resistor at the end of a transmission line or daisy chain bus (such as in SCSI), designed to match impedance and hence minimize reflections of the signal.  
• All resistors dissipate heat. This is the principle behind electric heaters.  

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Explain the terms real power, apparent power and reactive power for ac circuits and also the units used.

Explanation of terms real power, apparent power and reactive power for AC circuits:

Diagram: Power triangle relating apparent power to true power and reactive power.

Definition	Real Power	Apparent power	Reactive Power
	It is the product of voltage, current and power factor.	It is the product of voltage and current.	It is the product of voltage, current and sine of angle between the voltage and current.
Unit	Basic unit of real power is watt. i.e. Expressed as W or kW.	Basic unit of apparent power is volt- ampere. Expressed as VA (Volt Ampere) or KVA.	Has no other unit but expressed in VAR (Volt Ampere Reactive) or KVAR.
Formulas	Real power (P) = V I                                  (In DC circuits) P = VI Cosθ                         (in Single phase AC Circuits) P = √3 VL IL Cosθ         or P = 3 VPhIPh Cosθ (in Three Phase AC Circuits)	Apparent power (S) = V I Apparent Power = √ (True power2 + Reactive Power2) KVA = √KW2 + KVAR2	Reactive power (Q) = V I Sinθ Q =√ (Apparent Power2– True power2) VAR =√ (VA2 – P2) KVAR = √ (KVA2 – KW2)

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Compare JFET’s and MOSFET’s.

Comparison of JFET’s and MOSFET’s:

JFETs and MOSFETs are quite similar in their operating principles and in their electrical characteristics. However, they differ in some aspects, as detailed below :

JFETs vs MOSFETs
How it operates	JFETs	MOSFETs
	Voltage controlled	Voltage controlled.
Gain (Transconductance)	Low transconductance (gain)	Low transconductance (gain)
Input Impedance	JFETs are depletion type transistors only.	MOSFETs can be depletion type or enhancement type.
Input Impedance	JFETs offer less input impedance than MOSFETs. JFETs typically offer about 109 Ω of impedance.	MOSFETs offer greater input impedance. MOSFETs typically offer about 1014Ω of impedance, sometimes greater.
Cost	JFETs are somewhat cheaper to manufacture than MOSFETs. They have a less sophisticated manufacturing process.	MOSFETs are slightly more expensive to manufacture than JFETs.
Susceptibility to Damage	JFETs are less susceptible to damage from ESD because they have greater input capacitance than MOSFETs.	MOSFETs are more susceptible to damage from ESD because the metal oxide insulator that insulates the gate from the drain-source channel lowers the capacitance of the gate. This makes high voltage more able to break through and destroy the transistor.
Popularity	JFETs are less popular than MOSFETs.	MOSFETs are more popular and widely used today than JFETs.

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What is the Role of Capacitor in AC and DC Circuit?

Role of Capacitor in AC Circuits: 

In an AC circuit, capacitor reverses its charges as the current alternates and produces a lagging voltage (in other words, capacitor provides leading current in AC circuits and networks) 

Role and Performance of Capacitor in DC Circuit: 

In a DC Circuit, the capacitor once charged with the applied voltage acts as an open switch.

Rule of Capacitor in AC and DC Circuit

What is the Role of Capacitor in AC and DC Circuit?

Let’s explain in detail, but we will go back to the basics of capacitor first to discuss the matter.

What is Capacitor?

The capacitor is a two terminal electrical device used to store electrical energy in the form of electric field between the two plates. It is also known as a condenser and the SI unit of its capacitance measure is Farad “F”, where Farad is a large unit of capacitance, so they are using microfarads (µF) or nanofarads (nF) nowadays.

How Capacitor Works?

Working and Construction of a capacitor:

Whenever voltage is applied across its terminals, (Also known as charging of a capacitor) current start to flow and continue to travel until the voltage across both the negative and positive (Anode and Cathode) plates become equal to the voltage of the source (Applied Voltage). These two plates are separated by a dielectric material (such as mice, paper, glass, etc. which are insulators), which is used to increase the capacitance of the capacitor.

When we connect a charged capacitor across a small load, it starts to supply the voltage (Stored energy) to that load until the capacitor fully discharges.

Capacitor comes in different shapes and their value is measured in farad (F). Capacitors are used in both AC and DC systems (We will discuss it below).

Capacitance (C):

Capacitance is the amount of electric charge moved in the condenser (Capacitor), when one volt power source is attached across its terminal.

Mathematically,                 

Capacitance Equation:

C=Q/V

Where,

       C=Capacitance in Farads (F)

       Q=Electrical Charge in Coulombs

       V=Voltage in Volts

We will not go in detail because our basic purpose of this discussion is to explain the role and application/uses of capacitors in AC and DC systems. To understand this basic concept, we have to understand the basic types of capacitor related to our topic (as there are many types of capacitor and we will discuss capacitor types latter in another post because it is not related to the question).

Polar and Non-Polar Capacitor:

Non Polar Capacitor: (Used in both AC and DC Systems)

The Non Polar capacitors can be used in both AC and DC systems. They can be connected to the power supply in any direction and their capacitance does not effect by the reversal of polarity.

Polar Capacitor: (Only used in DC Circuits and Systems)

This type of capacitor is sensitive about their polarity and can be only used in DC systems and networks. Polar Capacitors don’t work in the AC system, because of the reversal of polarity after each half cycle in AC supply.

Types of Capacitors: Polar and Non Polar Capacitors with Symbols

Role of Capacitors in AC Circuits and System:

The capacitor has lots of applications in AC systems and we will discuss few uses of capacitor in AC networks below:

Transformer less power supply:

Capacitors are used in transformer less power supplies. In such circuits, the capacitor is connected in series with the load because we know that the capacitor and inductor in pure form does not consume power. They just take power in one cycle and deliver it back in the other cycle to the load. In this case, it is used to reduce the voltage with less power wastage.

Split phase induction motors:

The capacitors are also used in induction motor to split a single phase supply into a two phase supply to produce a revolving magnetic field in the rotor to catch that field. This type of capacitor is mostly used in household water pumps, Fans, air conditioner and many devices which need at least two phases to work.

Power Factor Correction and Improvement:

There are lots of advantages of power factor improvement. In a three phase power systems, capacitor bank is used to supply reactive power to the load and hence improve the power factor of the system. Capacitor bank is installed after a precise calculation. Basically, it delivers the reactive power which was previously traveled from the power system, hence it reduces the losses and improves the efficiency of the system.

Role of Capacitors in DC Circuits and system:

Power conditioning:

In DC systems, capacitor is used as a filter (mostly). Its most common use is converting AC to DC power supply in rectification (such as bridge rectifier). When AC power is converted into fluctuating (with ripples i.e. not a steady state with the help of rectifier circuits) DC power (Pulsating DC) in order to smooth and filter out these ripples and fluctuation, DC Polar capacitor is used. Its value is calculated precisely and depends on the system voltage and the demand load current.

Decoupling Capacitor:

Decoupling capacitor is used, where we have to decouple the two electronics circuits. In other words, the noise generated by one circuit is grounded by decoupling capacitor and it does not affect the performance of other circuit.

Coupling Capacitor:

As we know that Capacitor blocks DC and allows AC to flow through it (we will discuss it in the next session that how does it happens). So it is used to separate AC and DC signals (also used in the filter circuits for the same purpose). Its value is calculated in such a way that its reactance is minimized on the basis of frequency, which we want to pass through it. Coupling Capacitor is also used in filters (ripple remover circuits like RC filters) to separate AC and DC signal and removes the ripples from pulsating DC supply voltage to convert it into pure AC voltage after rectification.

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What is the difference between a battery and a capacitor?

While batteries and capacitors have similarities, there are several key differences. Like -

• Electrical energy in a Capacitor is stored in an electric field, where a Battery stores its electrical energy in a chemical form. 

• When a battery is discharging it, can be slower than a capacitor's ability to discharge because there is a latency associated with the chemical reaction to transfer the chemical energy into electrical energy. A capacitor is storing the electrical energy directly on the plates so discharging rate for capacitors are directly related to the conduction capabilities of the capacitor plates. 

• A capacitor is able to discharge and charge faster than a battery because of this energy storage method also. But unlike a battery that can turn its electrical current on and off, once a capacitor is connected to an outside circuit it will discharge as fast as it can until all the charge is drained. 

• Capacitors are much larger than a battery that stores equivalent charge. 

• The battery runs for longer time, but a capacitor discharges almost instantaneously. 

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What are data communication systems?

Data communication systems: A set of devices (hosts) connected by a communication medium that are able to share data through transmission over the media

•It is a combination of hardware and software that allows data communication to occur

•The effectiveness of data communication depends on four fundamental characteristic.

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Write down some common applications of Diodes.

Some common applications of Diodes: 

1. Power supply applications
2. AM (amplitude modulation) detectors
3. Back-EMF path
4. Clamping or DC restoration
5. Clipper or limiter
6. Non-linear circuits
7. Logic circuits

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