THEORY EXAMINATION (SEM–VIII) 2016-17 UTILIZATION OF ELECTRICAL ENERGY AND TRACTION

SECTION A – Basic Concepts of Utilization of Electrical Energy

Section A includes short questions that test the fundamental knowledge of electric traction, electric heating, illumination, refrigeration, and electrolysis. 

Question (a): What are the Various Traction Systems?

Answer:
Traction systems refer to methods used to drive vehicles such as trains and trams using electrical or mechanical power.

The main traction systems are:

Steam Traction – Uses steam engines powered by coal or fuel.

Diesel Traction – Uses diesel engines to produce mechanical power.

Electric Traction – Uses electric motors powered by electricity.

Hybrid Traction – Combination of diesel and electric systems.

Electric traction is widely used today because it is efficient, clean, and capable of providing high acceleration.

Question (b): What is the Special Advantage of Flywheel Drive?

Answer:
Flywheel drive is used to store energy in the form of rotational motion. The stored energy can be released when required.

The special advantage of a flywheel drive is that it provides a high amount of energy for short durations, which is useful for traction systems that require sudden bursts of power.

Flywheel drives also help reduce power fluctuations and improve system efficiency.

Question (c): What are the Various Current Collection Systems?

Answer:
Current collection systems are used in electric traction to supply electrical energy from the power source to the traction motor.

Common current collection systems include:

Overhead trolley wire system

Pantograph system

Third rail system

Conduit system

Among these, the pantograph system is widely used in modern electric trains.

Question (d): Write Any Three Advantages of Electric Heating

Answer:
Electric heating has several advantages compared to conventional heating methods.

Clean and pollution-free because no smoke or gases are produced.

Accurate temperature control is possible.

High efficiency because most electrical energy converts directly into heat.

Electric heating is widely used in industrial furnaces and domestic appliances.

Question (e): What is Arc Type Heating?

Answer:
Arc heating is a type of electric heating where heat is produced by an electric arc formed between two electrodes.

The arc produces extremely high temperatures, which are used for melting metals and other industrial processes.

Arc furnaces are commonly used in steel production.

Question (f): What are the Modes of Heat Transfer?

Answer:
Heat transfer occurs through three main modes:

Conduction – Heat transfer through solid materials by molecular vibration.

Convection – Heat transfer through fluids such as air or water.

Radiation – Heat transfer through electromagnetic waves without requiring a medium.

These mechanisms are important in designing heating and cooling systems.

Question (g): What is Faraday's Second Law of Electrolysis?

Answer:
Faraday’s second law states that when the same quantity of electricity passes through different electrolytes, the masses of substances liberated are proportional to their chemical equivalent weights.

This law is important in electroplating and electrochemical industries.

Question (h): Define Refrigeration

Answer:
Refrigeration is the process of removing heat from a substance or space to lower its temperature below the surrounding temperature.

Refrigeration systems are used in refrigerators, air conditioners, and cold storage units.

The process involves absorbing heat from the cooling space and releasing it to the surroundings.

Question (i): What is Luminous Flux?

Answer:
Luminous flux is the total quantity of visible light emitted by a light source per second.

It represents the perceived power of light and is measured in lumens (lm).

This parameter is important in illumination engineering for designing lighting systems.

Question (j): Define Welding

Answer:
Welding is a process of joining two or more metal pieces by heating them to a high temperature and allowing them to fuse together.

Electric welding uses electrical energy to generate heat for melting the metals.

Common welding methods include arc welding, TIG welding, and MIG welding.

SECTION B – Intermediate Concepts of Electrical Energy Utilization

Section B focuses on detailed explanations of heating systems, electrolysis applications, illumination laws, and traction systems. 

Question: Laws of Illumination and Requirements of Good Lighting

Answer:

Two important laws of illumination are:

1. Inverse Square Law

This law states that illumination is inversely proportional to the square of the distance from the light source.

If the distance from the source doubles, the illumination becomes one-fourth.

2. Cosine Law

According to the cosine law, illumination on a surface is proportional to the cosine of the angle between the incident light and the normal to the surface.

Requirements of Good Lighting

Good lighting should have the following characteristics:

Adequate brightness

Uniform illumination

Absence of glare

Proper color rendering

Minimum shadows

These factors help create comfortable and efficient working environments.

Question: Applications of Electrolysis

Electrolysis has many industrial applications.

Electroplating – Coating metals with another metal layer for protection.

Electrorefining – Purifying metals such as copper.

Electrometallurgy – Extracting metals from ores.

Production of chemicals – Manufacturing chlorine and hydrogen.

Electrolysis plays a major role in modern chemical and metallurgical industries.

Question: Types of Furnace for Induction Heating

Induction heating furnaces use electromagnetic induction to heat metal objects.

Two common types include:

Core-Type Induction Furnace

This furnace has a magnetic core similar to a transformer. It is used mainly for melting metals.

Coreless Induction Furnace

This furnace does not use a magnetic core and is commonly used for melting steel and other alloys.

Induction furnaces provide uniform heating and high efficiency.

Question: Classification of Electric Heating

Electric heating can be classified into several types:

Resistance Heating

Induction Heating

Arc Heating

Dielectric Heating

Infrared Heating

Each method is used for different industrial and domestic applications.

SECTION C – Advanced Concepts of Electrical Energy Utilization

Section C questions require deeper explanations of traction motors, refrigeration systems, and advanced heating methods. 

Question: Reversal of Direction of Traction Motor

The direction of rotation of a traction motor can be reversed by reversing the direction of current either in the armature or the field winding.

This is achieved using switching circuits or control systems.

Reversing the motor direction allows trains to move forward or backward.

Metadyne Control of Traction Motor

Metadyne control is a system used to regulate the speed and voltage of traction motors.

It uses a special type of DC generator called a metadyne, which can control large power using small control signals.

Advantages

Smooth speed control

Improved efficiency

Better voltage regulation

Disadvantages

Complex system

Higher maintenance requirement

Domestic Type Refrigerator

A domestic refrigerator works on the vapor compression refrigeration cycle.

The main components include:

Compressor

Condenser

Expansion valve

Evaporator

The refrigerant absorbs heat from the refrigerated space and releases it outside.

Difference Between Refrigerator, Water Cooler, and Air Conditioner

Induction Heating, TIG & MIG Welding, Plasma Arc Heating

Induction Heating

Induction heating uses electromagnetic induction to produce heat in conductive materials.

It is widely used in metal hardening, melting, and forging.

TIG Welding

TIG (Tungsten Inert Gas) welding uses a non-consumable tungsten electrode to produce the weld.

It provides high-quality welds.

MIG Welding

MIG (Metal Inert Gas) welding uses a consumable electrode wire that melts during welding.

It is faster and widely used in industrial applications.

Plasma Arc Heating

Plasma arc heating produces extremely high temperatures using ionized gas (plasma).

It is used in cutting and welding metals.

Conclusion

The utilization of electrical energy plays an important role in modern industries and domestic applications. Concepts such as electric traction, electric heating, refrigeration, illumination, and electrolysis demonstrate how electrical energy can be effectively used for different purposes.

Understanding these concepts helps engineers design efficient electrical systems and improve industrial processes.