Magnetism is the result of attraction, when two objects come together, or repulsion, when two objects move apart. A magnet is an object that has properties of magnetism. For example, a magnet might attract another object. A magnetic field is the invisible area around a magnet where magnetism occurs. And magnetized means that an object acquired magnetic properties.

Now, some substances can be super magnetic and others can be partially magnetic. Let’s take a look at three different types of substances: Ferromagnetic, Paramagnetic, and Diamagnetic 

Magnetic Substances: Diamagnetic Substances

The substances which are weekly magnetized when placed in an external magnetic field, in a direction opposite to the applied filed are called Diamagnetic Substances.

Example: Copper, lead, gold, silver, zinc, antimony, bismuth, etc.

Properties:

• These substances are repelled by magnet
• Atomic orbitals of these substances are completely filled
• It develops weak magnetization in a direction opposite to the direction of the applied magnetic field
• As soon as the magnetizing field removed, it loses its magnetization
• When placed in a non-uniform magnetic field, it tends to move from stronger to weaker regions of the magnetic field
• When placed in a uniform magnetic field, it aligns itself perpendicular to the direction of magnetic field
• Magnetic susceptibility is small negative value
• Relative permeability is close to one and always less than 1

Magnetic permeability is slightly less compared to free space.

Magnetic Substances: Paramagnetic Substances

The substances which are weekly magnetized when placed in an external magnetic field, in the same direction of the applied field are called Paramagnetic Substances.

Example: Sodium, aluminum, calcium, manganese, platinum

Properties:

• These substances are attracted by magnet
• Atomic orbitals of these substances are partially filled
• It develops weak magnetization in the direction of the applied magnetic field
• After removing the magnetizing field, it loses its magnetization
• When placed in a non-uniform magnetic field, it tends to move from weaker to stronger regions of the magnetic field
• When placed in a uniform magnetic field, it aligns itself in the direction of magnetic field
• Magnetic susceptibility is small positive value
• Relative permeability is close to one and always greater than 1
• Magnetic permeability is slightly more compared to free space

Magnetic Substances: Ferromagnetic Substances

The substances which are strongly magnetized when placed in an external magnetic field in the same direction to the applied field are called Ferromagnetic Substances.

Example: Iron, nickel, cobalt

Properties:

• These are characterized by parallel alignment of magnetic dipoles
• These substances are strongly attracted by magnet
• It develops strong magnetization in the direction of the applied magnetic field
• By removing magnetizing filed, it does not lose its magnetization
• When placed in a non-uniform magnetic field, it tends to move from weaker to stronger regions of the magnetic field
• When placed in a uniform magnetic field, it aligns itself parallel to the direction of magnetic field
• Magnetic susceptibility is much greater than 1
• Relative permeability is much greater than 1
• Magnetic permeability is much larger compared to free space.

Material	Magnetic Susceptibility (Xm­)	Relative Permeability (Km = 1 + Xm)	Magnetic Permeability (μm = Kmμ0)
Diamagnetic	-10-5 to -10-9	< 1	μm < μ0
Paramagnetic	10-5 to 10-3	> 1	μm > μ0
Ferromagnetic	≫ 1	≫ 1	μm ≫ μ0

Curie Temperature

It is the temperature above which ferromagnetic materials lose their permanent magnetic field and the magnetism completely disappears.

The magnetic susceptibility decreases with increase of temperature. So, the Ferromagnetism decreases with rise of temperature. It is maximum at absolute zero temperature and becomes zero at Curie temperature. Above this temperature the ferromagnetic material behaves as Paramagnetic substance.

Hope this article on Magnetic Substances was helpful for you. If you have any doubts/queries regarding the same you can let us know in the comment section below!

Performance Parameters in Power Plant are utilized to analyse the effective & efficient running of the machine while ensuring a degree of compliance with the statutory regulations. These include targeting factors like Power Generation, Economies of Power Generation, Load Curve, Load Duration Curve, Demand Factor, Diversity Factor, Load Factor, Connected Load, Maximum Demand, Average Load, Power Systems, Plant Capacity Factor and Plant Use Factor. In this article we will be covering the various performance parameters in power plant including Load Curve, Connected Load, Load Factor, Load Duration Curve & more in detail.

Variable load

The load on power station varies from time to time due to uncertain demands of the consumers and it is known as variable load on power station.

Effects of variable load

• Need of additional equipment
• Increase in production cost

 Load Curve

• The curve showing the variation of load on the power station with respect to time is known as a load curve.
• The load variations during a whole day are recorded half-hourly or hourly and are plotted against time on the graph. The curve obtained is known as daily load curve as it shows the variations of load during the day.
• The monthly load curve can be obtained from the daily load curves of that month. For this purpose average values of power over a month at different times of the day are calculated and then plotted on the graph. The monthly load curve is generally used to fix the rates of energy.
• The yearly load curve is obtained by considering the monthly load curves of that particular year. It is generally used to determine the annual load factor.

Importance of Load Curve

• The daily load curve shows the variations of load on the power station during different hours of the day
• The area under the daily load curve gives the number of units generated in the day

Units generated in a day = Area (in kWh) under daily load curve

• The highest point on the daily load curve represents the maximum demand on the station on that day.
• The area under the daily load curve divided by the total number of hours gives the average load on the station in the day.
• The ratio of the area under the load curve to the total area of rectangle in which it is contained gives the load factor.
• The load curve helps in selecting the size and number of generating units.
• The load curve helps in preparing operation schedule of the station.

Connected load: It is the sum of continuous ratings of all the equipment connected to supply system.

Maximum Demand: It is the greatest demand of load on the power station during a given period.

Average load: The average of loads occurring on the power station in a given period is known as average load or average demand.

Yearly average load = No of units (kWh) generated in a year/ 8760 hours

Demand factor

It is the ratio of maximum demand on the power station to its connected load.

Demand factor = Maximum Demand / Connected load

The value of the demand factor is usually less than 1. It is because maximum demand is always less than the connected load. The knowledge of demand factor is vital in determining the capacity of the plant equipment.

Diversity factor

The ratio of the sum of individual maximum demands to the maximum demand on power station is known as diversity factor.

• A power station supplies load to various types of consumers whose maximum demands generally do not occur at the same time. Therefore, maximum demand on the power station is always less than the sum of individual maximum demands of the consumer. Hence diversity factor is always greater than 1.
• The knowledge of diversity factor is vital in determining the capacity of the plant equipment.
• The greater the diversity factor, the lesser is the cost of generation of power. Because greater diversity factor means lesser maximum demand. Now, lower maximum demand means lower capacity of the plant which reduces the cost of the plant.

Load factor

The ratio of average load to the maximum demand during a given period is known as load factor.

Load factor = average load/maximum demand

If the plant is in operation of T hours

• The load factor may be daily load factor, monthly or annually if the period considered is a day or month or year.
• Load factor is always less than 1 because average load is smaller than maximum demand
• It plays a key role in determining the overall cost per unit generated.
• Higher the load factor of the power station, lesser will be the cost per unit generated. It is because higher load factor means lesser maximum demand. The station capacity is so selected that it must meet the maximum demand. Now, lower maximum demand means lower capacity of the plant which reduces the cost of the plant.

Plant capacity factor

It is the ratio of actual energy produced to the maximum possible energy that could have been produced during a given period.

The plant capacity factor is an indication of the reverse capacity of the plant. A power station is so designed that it has some reserve capacity for meeting the increased load demand in future. Therefore, the installed capacity of the plant is always somewhat greater than the maximum demand on the plant.

Reserve capacity = Plant capacity – Maximum demand

If the maximum demand on the plant is equal to plant capacity, then load factor and plant capacity factor will have the same value. In such case, the plant will have no reserve capacity.

Plant use factor

It is the ratio of kWh generated to the product of plant capacity and the number of hours for which the plant was in operation.

Capacity factor = Load factor × plant use factor

Load Duration Curve

When the load elements of a load curve are arranged in the order of descending magnitudes thus obtained is a load duration curve.

• The load duration curve gives the data in a more presentable form. In other words, it readily shows the number of hours during which the given load has prevailed.
• The area under load duration curve is equal to that of corresponding load curve. It gives the number of units generated in a period of time.

Hope this article on Performance Parameters in Power Plant was helpful for you. If you have any doubts/queries regarding the same you can let us know in the comment section below!

Frequency Response of Op-amp – An Introduction

The frequency response of amplifier refers to the band of frequencies or frequency range that the amplifier was designed to amplify.

Frequency Response of the op-amp: In open loop configuration, the gain of the op–amp is not constant and varies with the frequency and the product of gain and frequency remains constant till the unity gain frequency for the op–amp, which is known as the gain bandwidth product of the op–amp.

Gain – Bandwidth Product:

It is the bandwidth of the op-amp when the voltage gain is 1.

For 741: 1MHz (approx.)

Also called as:

• Closed loop bandwidth or
• Unity gain bandwidth or
• Small signal bandwidth

Equivalent Circuit of Op-Amp

 

• Op-amp can be modelled as Voltage Controlled Voltage Source (VCVS)
• Av_id = equivalent Thevenin voltage source
• R_o = Thevenin equivalent resistance looking back into the output terminal of op-amp
• V_o = Av_id = A (V₁ – V₂)
• v_id = Difference between voltage at non-inverting & inverting terminals
• Output voltage is proportional to the algebraic difference between the two input voltages.
• Polarity of the output voltage depends on polarity of difference between non-inverting and inverting input terminals

Ideal Voltage Transfer Curve

• Curve is almost vertical because of very large gain A
• Slope of the voltage transfer characteristic curve gives gain.

Frequency Response of Op-Amp

• Ideally infinite bandwidth

• This means ideally op-amp amplifies all the frequency with equal gain.
• But ideally gain depends on frequency

Gain depends on frequency because of capacitive components which are present due to:

• Junction Capacitance of FET & BJT at high frequencies
• Construction of op-amp using FET and MOSFET which forms MOS capacitance
• Interconnects used to connect different stages

These capacitance also limits the maximum frequency of operation of op-amp which is given by the slew rate.

To model all these capacitances in ideal model, we connect a capacitor at the output.

Practical Equivalent Model of Op-Amp:

Using Voltage Division:

Output voltage can be written as

Substituting the values

f = Operating frequency

From 0 Hz to f₀

• Open loop gain is almost constant from 0 Hz to cutoff frequency f

At f = f₀

• The voltage gain falls to 1/√2 times the initial value
• Power at this frequency falls to ½ times the maximum power.
• This is also called as 3 dB down frequency.

After f = f_o

• The gain decreases at 20 dB/decade or 6 dB/octave

From the Plot:

This frequency is called as Gain Cross Over frequency or Unity Gain Bandwidth of op-amp.

Gain Bandwidth Product of the-op amp is constant.

This means as the gain of the op-amp decreases, its cutoff frequency increases.

Ques. An op-amp has a closed loop gain of 40 dB and unity gain frequency of 1 MHz. The cutoff frequency of the op-amp is:

1. 1 kHz
2. 1 MHz
3. 10 kHz
4. 10 MHz

Ans. c

Solution:

A_CL = 40 dB = 100

f_u = GBP = 1MHz = 10⁶ Hz

f_u = ?

Since the gain bandwidth product is constant

A_CL × fc = G.B.P.

741 IC PIN-Diagram

• 8 Pin IC
• Pin 1 & 5 offset null pins.
• Pin 2 is inverting Input (V^–)
• Pin 3 is non-inverting Input (V⁺)
• Pin 4 is – V_EE supply
• Pin 6 is for Output
• Pin 7 is + V_cc supply
• Pin 8 is not connected and not used

741 IC derives its name:7 → Number of pins used4 → Number of inputs (inverting, non-inverting, +V_cc and -V_EE)1 → Number of outputs (only 1)Use of Offset Null Pins: DC Voltage at output when both input terminals are ground is called as output offset voltage.Output Offset Voltage Reasons

• Input bias current
• Input offset current
• Input offset voltage

The figure below shows the compensation technique to make the output offset voltage zero.Both the inputs of the op-amp are grounded and a 10k potentiometer is connected between the two offset null pins, the position of viper on potentiometer is adjusted till the output offset voltage becomes zero.

Circuit Elements RRB JE & SSC JE Study Notes – An Introduction

Electrical Network: A combination of various electric elements connected in any manner is called an electrical network.

Electrical Circuit

• An electrical circuit is a network which has a closed path that gives the return path for the flow of current.
• Electrical networks can either be closed or open but electrical circuits are only closed
• Hence every electrical circuit is a network, but all networks are not circuits.

Types of Circuit Elements – Notes for SSC JE & RRB JE

Active Element

• The elements that supply energy to the circuit is called an active element
• These have an ability to control the flow of charge
• Used for current control and voltage control applications
• Examples: Battery, voltage source, current source, diode

Passive Element

• The element which receives or absorbs energy and then either converts it into heat (R) or stored it in an electric (C) or magnetic (L) field is called passive element
• Do not need any form of electrical power to operate
• Not able to control the flow of charge
• Cannot amplify, oscillate, or generate an electrical signal
• Used for energy storage, discharge, oscillating, filtering and phase shifting applications
• Examples: Resistor, inductor, capacitor

Go through the table given below to know more about the other circuit elements with examples.

Voltage & Current Source

Ideal Voltage Source: An ideal voltage source has zero internal resistance.

Practical Voltage Source: A practical voltage source consists of an ideal voltage source (V_S) in series with internal resistance (R_S).

An ideal voltage source and a practical voltage source can be represented as shown in the figure.

Ideal Current Source: An ideal voltage source has infinite resistance. Infinite resistance is equivalent to zero conductance. So, an ideal current source has zero conductance.

Practical Current Source: A practical current source is equivalent to an ideal current source in parallel with high resistance or low conductance.

Ideal and practical current sources are represented as shown in the below figure.

Test your prepartion, right away –

Circuit Elements – Open & Short Circuit

Short Circuit: It is an electrical circuit that allows a current to travel along an unintended path with zero or very low electrical impedance. This results in an excessive amount of current flowing into the circuit.

Ideally, it has zero resistance hence high current will flow and no voltage drop across the terminals.

Open Circuit: It is a circuit where no current flows. Any circuit which does not have a return path to flow current is an open circuit.

It has infinite resistance, hence no current will flow.

Short circuit and an open circuit can be represented as shown in the figure.

Concept of Virtual Ground in Operational Amplifiers

Virtual Ground concept forms the basics of most of the Op-Amp applications. Often most of us know the definition of the virtual ground concept. i.e. the voltage at inverting terminal is equal to the voltage at not inverting terminal but the definition here is not complete. It does not specify the conditions where the virtual ground concept can be applied, or what are the limitations of the virtual ground concept. So here in this blog today we will discuss everything about the virtual ground starting from the basics and see the applications and utility of this concept.

An Op-Amp amplifies the difference of the voltages between the non-inverting and inverting terminal.

The gain of a practical open loop Op-Amp is infinite.

Mathematically:

For A_OL to be infinite there are two possibilities:

Since the output voltage of the Op-Amp is limited by its operating voltages (+V_cc and -V_EE),

The output voltage cannot be infinity.

The only possibility left is to make V_id approach zero:

V_id  =  V ⁺ – V ^– = 0

V ⁺  =  V ^–

i.e. voltage at inverting terminal follows the voltage non-inverting terminal.

This is only the half-truth, there are conditions when this statement is valid and there are conditions when this condition is not valid. Those conditions will be discussed in the blog.

Test Yourself Question:

Concept on Virtual Ground Study Notes – Download as PDF

The nervous system is a complex connection of nerves and unique cells (neurons) that are responsible for transmitting signals to and from various body parts.

Classification Of the Human Nervous System

The nervous system is basically classified into Central nervous system and Peripheral nervous system. The central nervous system manages the whole body and the nervous system. It is only because of the nervous system’s efficient coordination between the different organ systems that we can feel sensations like pain or cold.

1. The central nervous system (CNS) consisting of the brain, spinal cord.
2. The peripheral nervous system (PNS) consisting of sensory neurons, ganglia (a cluster of neurons) and nerves.

The nervous system is also classified on the basis of functionalityinto:

1. The somatic nervous system(SNS) responsible for conscious perception and voluntary motor response. For example, getting startled when someone sneaks up on you. That was not decided by you, nonetheless, it is a motor response involving skeletal muscle contractions.
2. The autonomic nervous system( ANS) responsible for involuntary body movements usually with the objective of maintaining body homeostasis. For example, sweating when your body is hot is to cool the body down.
3. The enteric nervous system(ENS) responsible for controlling smooth muscle and glandular tissue in the digestive system.

Let’s understand in detail the Central Nervous system and the Peripheral Nervous System –

Central Nervous System

So far you know that the nervous system is classified into Central and Peripheral nervous system. Neurons are the basic unit of the nervous system. These neurons are classified into three types – Sensory, motor and association/connecting neurons. The main function of the central nervous system is to keep control over the entire body and the nervous system. The Central Nervous consists of two main parts – Brain and Spinal Cord. These two parts are covered by three membranes mentioned below:

• Durameter which is the outer layer/membrane.
• Arachnoid membrane is the middle layer.
• Piameter is the innermost membrane

Let’s study in details the two main parts of the central nervous system i.e. brain and spinal cord –

Brain

It is entirely covered by a protective layer called meninges. To protect the brain from injuries it is covered by a bony box termed as the cranium. Furthermore, the brain is divided into three parts Forebrain, Midbrain, and Hindbrain.

• Forebrain

The forebrain is made up of the Cerebrum, Thalamus, and Hypothalamus. The Cerebrum is associated with memory, wisdom, knowledge, will power and thinking. Thalamus regulates cold, heat and pain. Whereas, the Hypothalamus controls the sweat, blood pressure, secretion of hormones, thirst, hunger, etc.

• Midbrain

Midbrain manages the main function of hearing and vision.

• Hindbrain

Hindbrain includes parts like Cerebellum, Pons and Medulla. The human body posture is managed by Cerebellum. The Pons acts as a bridge between the spinal cord and brain. Medulla regulates important functions like respiration, heart rate, sneezing, and coughing, etc.

Spinal Cord

• The spinal cord starts from the medulla oblongata and extends towards the neural canal of the backbone/vertebral column.
• There are 31 pair of spinal nerves that arises from the side of the spinal cord.
• The function of the Spinal cord is to control all the reflexes that take place below the neck.
• Furthermore, the spinal cord conducts the sensory impulses arising from the muscles and skin to the brain.
• Vertebrae protect the spinal cord from any kind of injuries.
• The spinal cord also conducts the motor responses from the brain to the muscles present in the limbs and trunk area.

Peripheral Nervous

The peripheral nervous system consists of the nerves that arise from the brain and spinal cord. The human body has 31 pairs of spinal nerves and 12 pairs of cranial nerves. The peripheral nervous system is divided into the somatic nervous system and autonomic nervous system.

Somatic Nervous system

Somatic Nervous system includes the peripheral nerve fibers that convey the sensory information to the motor nerve fiber and central nervous system.

Autonomic Nervous system

The autonomic nervous system consists of three sections namely, the sympathetic, parasympathetic and the enteric nervous system. It regulates the smooth muscle of the viscera (internal organs) and glands.

What is the Function of the Nervous System?

• Essentially, the primary function of the nervous system is to send signals either from one cell to another or from one body organ to another.
• There is more than one way in which cells send signals. The broadcast method of signaling is done through the endocrine system where the hormones are released into the circulatory system. Through the nervous system, the signaling is done “point to point”. Hence, the nervous system entails advantages of being more specific, accurate and speedy.
• The human nervous system controls the human body. The body reacts to stimulus because the nervous system extracts these external signals via sensory receptors and the central nervous system processes these signals and decides on an appropriate response and then sends an output signal to the concerned body part to activate the response.

Diseases Associated with the Nervous System

Diseases occurring in the nervous system are mainly due to a genetic defect, a result of traumatic experiences, infections, or ageing. Diseases associated with the peripheral nervous system are mainly due to stoppage in nerve conduction. Illustrated below is the list of diseases along with their symptoms, treatment and precautionary measures.

This note on one of the most vital systems of the human body will help you in your static GK preparation. However, it is important for the candidate to be prepared with the other human body processes as all work hand-in-hand.