# Polytechnic EEE Notes || Fundamentals Of Electrical & Electronics Engineering (EEE) Notes 3rd Sem

Fundamentals Of Electrical & Electronics Engineering (EEE): Fundamentals of Electrical and Electronics Engineering (EEE) is a branch of engineering that deals with the study of electric circuits, electric power, and electrical and electronic devices.

The subject covers various topics such as circuit analysis, electrical machines, power electronics, digital electronics, control systems, electrical materials, and electromagnetic fields. In this article Polytechnic EEE Notes are available. Fundamentals Of Electrical & Electronics Engineering (EEE) Notes for polytechnic students.

## Polytechnic EEE Notes || Fundamentals Of Electrical & Electronics Engineering (EEE) Notes

Polytechnic EEE Notes || Fundamentals Of Electrical & Electronics Engineering (EEE) Notes

### Q. Define insulator and conductor. Give examples of each.

Ans: An insulator is a material that does not allow an electric current to flow easily. An example of an insulator is rubber or plastic. A conductor is a material that allows electric current to flow easily. An example of a conductor is copper or aluminum.

### Q. State Ohm's law.

Ans: Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance between them. Mathematically, it can be expressed as V = IR, where V is the voltage, I is the current, and R is the resistance.

### Q. Describe the construction of a DC generator.

Ans: A DC generator is a device that converts mechanical energy into electrical energy. It consists of a rotating armature that is coiled with wire, a stator that is stationary, and a commutator that helps to maintain the current direction in the coils. The armature rotates in a magnetic field created by the stator, which induces an electromotive force (EMF) in the coils. The commutator ensures that the EMF created in each coil is positive and directed out of the positive terminal.

### Q. Define the back emf of a DC motor.

Ans: The back EMF of a DC motor refers to the electromotive force (EMF) generated in the armature of the motor when it rotates. It opposes the applied voltage and current in the armature, reducing the net current and torque in the motor. Back EMF helps to regulate the speed of the motor and to prevent it from overheating.

### Q. Define the terms: time period, frequency, and RMS value of an alternating quantity.

Ans: The time period of an alternating quantity is the time taken by the quantity to complete one full cycle of its motion.

Frequency is the number of cycles of an alternating quantity completed in one second.

The RMS (Root Mean Square) value of an alternating quantity is a measure of its effectiveness or heating value and is equal to the square root of the mean of the squares of the values of the alternating quantity. It represents the equivalent steady DC voltage or current that produces the same heating effect as the alternating quantity.

### Q. Write in detail about the construction of a single-phase transformer.

Ans: Construction of a Single-Phase Transformer: A single-phase transformer is a passive electrical component that transforms electrical energy from one circuit to another through electromagnetic induction. It is used to either step up or step down the voltage level. The construction of a single-phase transformer is as follows:

Core: The core of a single-phase transformer is made of laminated iron sheets that are stacked together. This helps to reduce core losses and improve the efficiency of the transformer.

Windings: The two windings of a single-phase transformer are called the primary winding and the secondary winding. The primary winding is connected to the input voltage source and the secondary winding is connected to the load. The windings are made of copper wire and are insulated from each other.

Insulation: The windings of a single-phase transformer are insulated from each other and from the core using a layer of insulating material such as varnish, paper, or plastic. This helps to prevent electrical short circuits and to improve the safety of the transformer.

Protective Cover: A protective cover is placed over the core and windings to prevent damage to the transformer from moisture, dust, or other environmental factors.

### Q. What are the various methods of house wiring?

Ans: House wiring refers to the electrical wiring and connections that are installed in a building for lighting, power, and communication purposes. There are several methods of house wiring, including the following:

• Series Wiring: In this method, all the electrical devices are connected in a series, one after the other. This method is simple, but not efficient as a failure in any device would result in the failure of all devices connected in the series.
• Parallel Wiring: In this method, each device is connected to its own electrical supply and they all run parallel to each other. This method is more efficient as a failure in one device does not affect the other devices connected in parallel.
• Radial Wiring: In this method, the electrical supply is connected to the devices from a single point and all the devices are connected in a radial pattern. This method is commonly used in residential buildings.
• Loop Wiring: In this method, each device is connected to the next device in a loop. This method is commonly used in commercial buildings.

### Q. Differentiate between intrinsic and extrinsic semiconductors.

Ans: Intrinsic vs Extrinsic Semiconductor: An intrinsic semiconductor is a pure form of a semiconductor material such as silicon or germanium, while an extrinsic semiconductor is a semiconductor material that has been doped with impurities such as boron or phosphorus to increase its conductivity.

The main difference between intrinsic and extrinsic semiconductors is that intrinsic semiconductors have very low conductivity, while extrinsic semiconductors have higher conductivity due to the presence of impurities.

Intrinsic semiconductors are used in devices such as solar cells, while extrinsic semiconductors are used in devices such as transistors and diodes.

### Q. Describe the p-n junction diode.

Ans: P-N Junction Diode: A p-n junction diode is a type of semiconductor device that allows current to flow in one direction only. It is made up of a p-type semiconductor material and an n-type semiconductor material that are joined together to form a p-n junction.

The p-type semiconductor material has an excess of positive charge carriers (holes) and the n-type semiconductor material has an excess of negative charge carriers (electrons). When a voltage is applied across the p-n junction, it creates a potential barrier that only allows current to flow in one direction.

### Q. What are the various biasing circuit configuration of an NPN transistor?

Ans: There are several biasing circuit configurations for NPN transistors, including:
• Collector-Base Bias: In this configuration, a voltage divider network is used to establish a voltage between the collector and base terminals. This configuration is simple and commonly used.
• Emitter Bias: In this configuration, a resistor is used in series with the base terminal, and the emitter is biased by a voltage source. This configuration provides better stability compared to Collector-Base Bias.
• Voltage Divider Bias: This is a variation of the Collector-Base Bias configuration, in which the voltage divider network is connected to the collector terminal, with the base terminal being connected to the midpoint of the voltage divider.
• Collector Feedback Bias: In this configuration, a part of the collector current is fed back to the base terminal, resulting in stable biasing.
• Darlington Pair Bias: In this configuration, two NPN transistors are connected in a Darlington configuration, which provides a high current gain and is used in applications requiring high current amplification.
These are the most common biasing circuit configurations for NPN transistors. The choice of biasing configuration depends on the specific requirements of the application, such as stability, current gain, and power dissipation.

### Q. Write the differences between insulators and conductors.

Ans: Insulators and conductors are materials that have different electrical properties. An insulator is a material that does not allow the flow of electric current through it easily, whereas a conductor is a material that allows the flow of electric current through it with minimal resistance. The main difference between insulators and conductors is their electrical conductivity.

### Q. State Kirchoff's Voltage Law and explain it.

Ans: Kirchhoff's Voltage Law (KVL) states that the sum of the voltages around any closed loop in a circuit must be equal to zero. In other words, the total voltage gained around the loop must equal the total voltage lost. This law helps to determine the voltage drops and potential differences in a circuit.

### Q. Define self-inductance and mutual inductance.

Ans: Self-inductance is the property of a coil or an inductor by which it opposes the change in current flowing through it. It results in the production of a back-emf in the coil, proportional to the rate of change of current. On the other hand, mutual inductance is the property of two or more coils that are physically close to each other and are capable of inducing a voltage in each other.

### Q. State the differences between a series circuit and a parallel circuit.

Ans: A series circuit is a type of electrical circuit where components are connected end-to-end to form a single path for current flow. In contrast, a parallel circuit is a type of electrical circuit where components are connected in such a way that the same voltage is applied to all components, but the current flowing through each component may be different. The main difference between series and parallel circuits is the way components are connected and the distribution of current in the circuit.

### Q. Define work, energy, and power. Also, deduce 1 kWh = 860 kcal.

Ans: Work is the transfer of energy from one object to another, done when a force is applied over a certain distance. Energy is the capacity to do work, and it can take many forms, including mechanical, thermal, electrical, and so on. Power is the rate at which work is done and is measured in watts (W). 1 kilowatt-hour (kWh) is equivalent to 3.6 million joules, and 1 kilocalorie (kcal) is equivalent to 4184 joules, so 1 kWh = 860 kcal.

### Q. Define the power factor of an AC circuit.

Ans: The power factor of an AC circuit is the ratio of real power to apparent power. Real power is the power that is actually used to perform work, and apparent power is the product of the current and voltage in a circuit. A power factor of 1 means that all the power is being used effectively, while a power factor of less than 1 means that some of the power is being wasted due to power losses in the circuit.

### Q. Deduce the emf equation of a DC generator.

Ans: The emf equation of a DC generator can be derived using Faraday's Law of Electromagnetic Induction. According to Faraday's Law, the emf induced in a conductor is proportional to the rate of change of magnetic flux linking the conductor.
The emf equation of a DC generator can be represented as:

e = -N dΦ/dt

where e is the emf, N is the number of turns in the coil, and dΦ/dt is the rate of change of magnetic flux.

### Q. Write three industrial applications of DC generator and DC motor.

Ans: Industrial applications of DC generators and DC motors include:
• Power Generation: DC generators are used to generate electricity in power plants.
• Electric Traction: DC motors are used to drive electric trains and trams.
• Steel Industry: DC generators and motors are used to drive rolling mills and cranes in the steel industry.

### Q. Deduce the emf equation of a transformer.

Ans: The emf equation of a transformer can be derived using Faraday's Law of Electromagnetic Induction. The emf induced in the secondary coil of a transformer is proportional to the rate of change of magnetic flux linking the coil, which in turn is proportional to the current in the primary coil.
The emf equation of a transformer can be represented as:

e2 = -N2 dΦ/dt = -N2 (Φ1 / L1) di1/dt

where e2 is the emf induced in the secondary coil, N2 is the number of turns in the secondary coil, Φ1 is the magnetic flux in the primary coil, L1 is the inductance of the primary coil, and di1/dt is the rate of change of current in the primary coil.

### Q. Mention some of the characteristics of a series circuit.

Ans: Characteristics of a series circuit:
• The same current flows through all components in a series circuit.
• The sum of the voltage drops across the components in a series circuit is equal to the total voltage.
• The total resistance of a series circuit is equal to the sum of the individual resistances.
• The total power in a series circuit is constant and is equal to the power supplied by the voltage source.

### Q. State and explain Kirchhoff's Laws.

Ans: Kirchhoff's Laws are two fundamental laws of electrical circuits:

• Kirchhoff's Current Law (KCL): It states that the total current flowing into a junction must equal the total current flowing out of the junction. Mathematically, it can be represented as:
ΣIin = ΣIout
• Kirchhoff's Voltage Law (KVL): It states that the sum of the voltage drops in a loop must equal the total voltage supplied to the loop. Mathematically, it can be represented as:
ΣVdrop = 0

### Q. Describe the construction of a DC motor.

Ans: A DC motor consists of a rotor (rotating part) and a stator (stationary part). The stator has a permanent magnet and the rotor has a coil, which rotates inside the magnetic field. The stator also has a commutator and brushes, which provide the rotating coil with a continuous supply of current.

When the current flows through the coil, a magnetic field is generated, which interacts with the magnetic field of the permanent magnet, causing the rotor to rotate. The commutator and brushes ensure that the current flows in the correct direction in the coil so that the magnetic field generated by the coil continues to rotate the rotor.

### Q. Define the following terms:

AC Time period, RMS value, Peak value, and Form factor.

Ans:
• AC Time period: The time taken by an alternating current (AC) waveform to complete one full cycle. It is represented by T and is measured in seconds.
• RMS value: The root means square (RMS) value of an AC waveform is a measure of its effectiveness or heating value. It is equivalent to the DC value that would produce the same amount of heat in a resistor as the AC waveform. The RMS value is equal to the magnitude of the AC waveform divided by the square root of 2.
• Peak value: The peak value of an AC waveform is the maximum amplitude that the waveform reaches in one direction during a cycle. It is represented by Vp.
• Form factor: The form factor of an AC waveform is the ratio of its RMS value to its peak value. It provides a measure of the waveform's non-uniformity.

### Q. Describe the operation of a Transformer.

Ans: Transformer: A transformer is a passive electrical device that transfers electrical energy from one electrical circuit to another, by means of electromagnetic induction. The operation of a transformer involves the interaction between a primary coil and a secondary coil that is magnetically coupled. When an AC voltage is applied to the primary coil, an alternating magnetic flux is generated, which induces an AC voltage in the secondary coil. The ratio of the number of turns in the primary coil to the number of turns in the secondary coil determines the transformation ratio of the transformer.

### Q. Explain the operation of a PNP transistor. How many types of transistor biasing are there? Name them.

Ans: PNP transistor: A PNP transistor is a type of bipolar junction transistor (BJT) that consists of a p-type semiconductor material sandwiched between two n-type semiconductor regions. The operation of a PNP transistor involves controlling the current flowing through the base-emitter junction. When a positive voltage is applied to the base, a small current flows, which controls the larger current flowing from the collector to the emitter. There are two main types of transistor biasing:

• Base Bias: In base bias, a combination of resistors is used to provide a stable base current.
• Collector Feedback Bias: In collector feedback bias, a portion of the collector current is fed back to the base terminal to control the base-emitter current.

### Q. What is a rectifier? Describe the operation of a full wave Bridge rectifier.

Ans: Rectifier: A rectifier is an electrical device that converts an alternating current (AC) into a direct current (DC). There are several types of rectifiers, including half-wave, full-wave, and bridge rectifiers.

Full-wave Bridge rectifier: A full-wave bridge rectifier consists of four diodes connected in a bridge configuration. It converts an AC input waveform into a full-wave rectified DC output waveform. The operation of a full-wave bridge rectifier involves two half-wave rectification processes, where each diode conducts for half of the input waveform cycle, providing a full-wave rectified output.

### Q. What is a semiconductor? What are the different types of biasing in a PN junction diode?

Ans: Semiconductor: A semiconductor is a material with an electrical conductivity that lies between that of a conductor and an insulator. Examples of semiconductors include silicon and germanium.

PN junction diode: A PN junction diode is a two-layer semiconductor device, consisting of a p-type material and an n-type material. There are two types of biasing in the PN junction diode:

• Forward Bias: In forward bias, the p-type material is connected to the positive terminal of the voltage source, and the n-type material is connected to the negative terminal, providing a forward voltage across the junction.
• Reverse Bias: In reverse bias, the p-type material is connected to the negative terminal of the voltage