Category: Physics Notes PPT

The continuity equation describes the nature of the movement of physical quantities. The continuity equation is usually applied to the conserved quantities, but it can also be generalized for the extensive quantities. Quantities like mass, momentum, energy and electric charge are some major conserved quantities. The continuity equation can be applied to these quantities to describe nature and other physical phenomena.

 

The continuity equation plays a significant role while studying the movement of fluids, especially when fluid is passed through a tube of varying diameters. Normally the fluids which are taken into consideration have a constant density and are incompressible. This concept can be related to the human body in several aspects.

 

For example, the blood vessels or arteries are divided into several capillaries, which then join to form a vein. The continuity equation can calculate the speed of the blood flowing through the blood vessels. Since the blood vessels are elastic, several other factors are to be applied with the continuity equation precisely to make the proper calculation. This includes the elasticity and the diameter of the blood vessels.

 

To the understand continuity equation; let’s consider the flow rate f first:

 

f=Av

 

Where,

f = flow rate

A = the cross-sectional area of a point in the pipe

v = the average speed at which a fluid is moving inside the pipe.

 

The flow rate is the amount of liquid that passes from a particular point in a unit of time. For example, the amount of water (in volume) coming out from a pipe per minute. The unit of flow rate is usually calculated in terms of milliliters per second.

 

The application of the continuity equation can be seen while calculating the amount of blood that the heart pumps into the vessels, thus determining a person’s health condition. This process is also helpful in determining whether a blood vessel is clogged, and taking further measures against heart issues.

 

Derivation of Continuity Equation Assumption

The following points are the assumptions of the continuity equation:

• The tube, which is taken into consideration, has a single entry and a single exit.

• The fluid that flows in the tube is non-viscous.

• The fluid is incompressible.

• Fluid flow is steady.

 

Derivation of Continuity Equation 

Let us consider the following diagram:

 

 

Let us consider that the fluid flows in the tube for a short duration Δt. During this time, the fluid will cover a distance of Δx₁, with a velocity of v₁in the lower part of the pipe. 

 

The distance covered by the fluid with speed v₁ in time Δt will be given by,

 

Δx₁ = v₁Δt

 

Now, in the lower part of the pipe, the volume of fluid flows into the pipe is,

 

V = A₁Δx₁ = A₁ v₁Δt

 

We know that mass (m) = Density (ρ) × Volume (V). So, the mass of fluid in region Δx₁ will be:

 

Δm1= Density × Volume

 

⇒ Δm1  =ρ₁A₁v₁Δt ——–(Equation 1)

 

Now, we have to calculate the mass flux at the lower part of the pipe. Mass flux is the total defined mass of the fluid that flows through the given cross-sectional area per unit of time. For the lower part of the pipe, with the lower end of pipe having a cross-sectional area A₁, the mass flux will be given by,

 

Δm1/Δt   =ρ₁A₁v₁——–(Equation 2)

 

Similarly, the mass flux of the fluid at the upper end of the pipe will be:

 

Δm2/Δt   =ρ₂A₂v₂——–(Equation 3)

 

Where,

v₂ = velocity of the fluid flowing in the upper end of the pipe.

Δx₂= distance traveled by the fluid.

Δt  = time, and

A₂ = area of a cross-section of the upper end of the pipe.

 

It is assumed that the density of the fluid in the lower end of the pipe is the same as that of the upper end. Thus, the fluid flow is said to be streamlined. Thus, the mass flux at the bottom point of the pipe will also be equal to the mass flux at the upper end of the pipe. Hence Equation 2 = Equation 3.

 

Thus, 

 

ρ₁A₁v₁ = ρ₂A₂v₂ ——–(Equation 4)

 

Based on equation 4 it can be stated that:

 

ρ A v = constant

 

The above equation helps to prove the law of conservation of mass in fluid dynamics. As the fluid is taken to be incompressible, the density of the fluid will be constant for steady flow.

 

So, ρ₁ = ρ₂

 

Applying this to Equation 4; it can be written as:

 

A₁v₁ = A₂v₂

 

The generalized form of this equation is:

 

A v = constant

 

Now, let’s consider R as the volume flow rate, hence the equation can be expressed as:

 

R = A v = constant

 

This is the derivation of the continuity equation.

Heavy hydrogen, often known as deuterium, is one of the stable isotopes of hydrogen. Deuterium gets its name from the Greek word deuterons, which means “second.” 

The stable isotopic variation of hydrogen gas has only one proton and one neutron. Protium, which does not have a neutron, makes up 99.9% of naturally occurring marine hydrogen, while Deuterium makes up only 0.02 percent.

Harold C. Urey, an American scientist, and his coworkers Ferdinand G. Brickwedde and George M. Murphy discovered deuterium in 1931. Urey anticipated that the vapor pressures of molecular hydrogen (H₂) and a corresponding molecule with one hydrogen atom substituted by deuterium (HD) would differ, allowing them to be separated by liquid hydrogen distillation.

What is Deuterium?

Deuterium, also known as heavy hydrogen, is one of the isotopes of hydrogens that is stable. The name deuterium is derived from the Greek word deuterons, which means ‘second’.  The nucleus of the hydrogen-deuterium atom is known as a deuteron, containing one proton and one neutron. Protium does not have a neutron. Deuterium has a natural abundance of about one atom in between 6420 hydrogens in the oceans. Thus, deuterium takes account for approximately 0.02% (0.03% by mass) of all the hydrogens that occur naturally in the oceans, and protium takes account for the rest of 99.98%.

Deuterium Oxide

Deuterium oxide is an isotopic form of water which is always stable and non-radioactive. This element contains two atoms of deuterium (D) and one atom of oxygen, with DNA-labelling activity. It is also known as heavy water. It is called heavy water due to the presence of deuterium in it, which is a heavier hydrogen isotope as compared to the hydrogen isotope (protium), which is present in normal water.

The heavier hydrogen isotope brings out the nuclear properties of water. The increase in the mass of the water due to deuterium makes the water slightly different from normal water in terms of physical and chemical properties.

Facts, Properties and Uses

Properties

Deuterium has several properties as listed below:

1. Deuterium forms chemical bonds that are stronger than regular hydrogen.The triple point, boiling point, vapor pressure, heat of fusion, and heat of evaporation of deuterium are all much higher than those of common hydrogen.

2. The gas deuterium is colorless. When ionized, however, it gives off a distinctive pink hue.

3. Because of the stronger connections, heavy water has a density of 10.6 times that of conventional water (1.624 g/cm3). In standard water, heavy water ice sinks, but it floats in heavy water.

4. Heavy water has a higher viscosity than regular water. (12.6 μPa·s at 300 K).

Uses

• Deuterated water is used in Magnetic Resonance Spectroscopy.

• It is used as a moderator in nuclear reactors.

• The metabolic rate of the human body can be determined by using it.

• For tracking the process of Photosynthesis in plants, it is used as the primary tracer element.

• By using Deuterium in Nuclear Magnetic Resonance Spectroscopy, magnetic field stabilization is being maintained.

• It is used in the determination of the isotopologue of various organic compounds.

• In heavy water form, it is used in Infrared Spectroscopy.

• There is an important aspect of Nuclear fusion reaction known as Tritium. It is controlled by using Deuterium.

Facts

Atomic weight = 2.014

Molecular weight = 4.0282 g/mol

Symbolic representation = 2H

Boiling point = (-)249^o C

Melting point = (-)254^o C

• Delton or Deuteron is the name for a single Deuterium nucleus. Deuterium has no radioactive effects due to its minute presence among the naturally occurring Hydrogen form.

• It is naturally flammable and emits a pale blue flame.

• It is non-toxic, however, it can deplete oxygen levels in the atmosphere, resulting in asphyxiation.

• It is also referred to as Hydrogen 2 and Deuterons.

• It has no color and odor.

• By nature it is non-corrosive.

• When the temperature is low, it is slightly soluble in water (cold water)

In FM, a radio wave known as the “carrier” or “carrier wave” is modulated in frequency by the signal that is to be transmitted. However, the amplitude and the phase constant remain constant in the case of frequency modulation. While amplitude modulation or AM is a technique that we use in electronic communication, most commonly for transmitting information through a radio carrier wave. 

Additionally, there is a term that is one of the two principal forms of angle modulation alongside frequency modulation, and it is called phase modulation. PM is a modulation pattern that we use for conditioning communication signals for transmission.

This page will help you distinguish between amplitude modulation and frequency modulation. Also, you will get to learn the difference between FM, AM, and PM modulation in tabular form. 

 

How does FM Work?

Frequency modulation works by continuously changing the strength of the transmitted signal in relation to the information being sent.

FM radio uses frequency modulation. However, to understand frequency modulation, assume a signal with a low frequency and amplitude. As the signal passes, its frequency remains unchanged or unmodulated. We find that a signal carries very little information.

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So, when you introduce information to this signal, there’s a variation to the frequency that varies directly with the information. Also, when the frequency is modulated between low and high, the carrier frequency transmits music or voice. Therefore, we find that the frequency changes as a result, but the amplitude remains constant the entire time.

For example, the changes in the strength of the signal may be utilized to specify the sounds to be reproduced by the speaker, or the light intensity of television pixels.

How does an AM Work?

While receiving input signals, an AM receiver discovers amplitude variations in the radio waves at a specific frequency. It amplifies changes in the signal voltage to operate a loudspeaker or earphone.

Working principle of an AM receiver in reality:

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In this, a radio receiver is present in the opposite of a radio transmitter that uses an antenna to capture radio waves. Further, it processes those waves to elicit only those waves that are vibrating at the needed frequency and filters the audio signals that were added to those waves, following, amplifying the audio signals, and finally plays them on a speaker.

How does PM Work?

Phase modulation encodes a message or an input signal as variations in the instantaneous phase of a carrier wave.

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In phase modulation, the working principle is that the instantaneous amplitude of the baseband signal modifies the phase of the carrier signal thereby keeping the constant amplitude and frequency. The phase of a carrier signal is modulated by phase modulation to follow the altering signal level or amplitude of the message signal. 

Furthermore, the peak amplitude and the frequency of the carrier signal are also kept constant. However, as the amplitude of the message signal alters, the phase of the carrier also changes.

Difference between AM and FM

Below is the table of AM versus FM:

Difference between AM, FM, and PM

For a radio signal to carry audio or other information for broadcasting or for two-way radio communication, signals must be modulated or changed in some way. Though we have several ways in which a radio signal may be modulated, one of the easiest is to change its amplitude in line with variations of the sound. Here, we discussed three types of modulation, viz: FM, AM, and PM, which will help you understand the basics of the modulation along with the difference between each. 

Generally, discovery is recognizing or finding something that already exists for the first time that nobody had even heard about or found before, e.g. how Christopher Columbus discovered America. On the other hand, an invention is creating or forming something totally new with one’s own ideas, knowledge, interest, and development and hence inventions are considered unique always.

Definition

Discovery: A discovery is a process of identifying and recognizing something that already exists, for the first time, that nobody has ever found before.

E.g., how Christopher Columbus discovered America.

Invention: An invention is, on the other hand, a process of creating something totally new and unique with one’s own ideas and development.

Discovery and invention have come a long way, and students have often been confused between the two. However, you should note that there is a significant difference between invention and discovery. To understand the difference, it is vital to have a prior understanding of the terms individually.

Although both these terms, discovery and invention, indicate bringing of something new in the limelight or forefront, they differ at their grassroots. You have to understand the relevant points of distinction in order to delve deeper into their individual concepts. 

Besides, make sure you are aware of the proper example for both of these terms. It will help you in clearing your doubts properly. Examples have always served a vital purpose when it comes to understanding a specific concept.

How Do You Differentiate Between Discovery and Invention?

To understand what is the difference between invention and discovery, examples are the simplest methods. However, it is important to understand the terms from their grassroots so that you can develop a better understanding of the advanced concepts.

 

Here is a Table for Showcasing the Difference Between Discovery and Invention for Your Convenience –

 

Here, the above table shows the difference between invention and discovery. Students need to go through these points thoroughly for a better understanding.

 

For more information on invention and discovery difference, you can look into our online programs. These are drafted by eminent faculties and you can develop your understanding to a new height.

 

So, get your study lessons and boost your preparation right away. You may also download our app for advanced learning.

Conclusion

Topics like invention-discovery differences, where they are almost similar and are often confused, should be dealt with examples. It will not only help in clearing the doubts but also help students in building the foundation for each topic.

LCD

LCD stands for liquid crystal display. Liquid crystal is a kind of material that is neither liquid nor a solid, it comes in between these two states of matter. It has properties similar to that of the crystallised solid. The arrangement of molecules is in a fixed pattern however they are not fixed in shape or form.

LED

LED stands for light-emitting diode and it is a semiconductor light source that emits light when current flows through it.

It is a type of flat-panel display that uses an array of light-emitting diodes as pixels for displaying images.

It comprises two sheets of polarising material with a liquid crystal solution between them.

Full-Form of LCD and LED

LCD

This technology is used in laptops, digital clocks, watches,  digital cameras, watches, etc.

There are three types of LCD TVs

1. Flat-screen LCDs

2. Front projection LCDs

3. Rear projection LCDs

LED

They are usually found in smartphones, televisions, computer monitors and instrument panels and use a liquid crystal display panel to control where the light is displayed on your screen.

There are 3 types of LEDs based on their backlighting methods:

1. Edge-LEDs

2. Dynamic RGB LEDs

3. Full-array LEDs

Working Principle of LCD Monitor

To display anything on the screen, three major components are necessary, they are

1. Light: A source through which you see the objects.

2. Colour: To view the objects in different colours otherwise everything on the screen will appear white.

3. A way to control the light and colour on the screen.

These three components are found in LCD. 

LCD  uses liquid crystals in its main form of functioning to produce a visible image.

Principle

It is a type of flat-panel display technology that uses diodes, small cells and ionised gases for the production of images.

LCD works on the principle of blocking light.

It also works on the modulating property of light where light modulation is the technique of sending and receiving the signal through the light. 

Working

A light is non-polarized by nature when passed via a plane. It scatters in different directions and phases as you can see in the image below:

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On placing the polarization filter (either horizontal or vertical) and passing the same light through this filter. 

The filter would polarise the light in one phase and produce a clean polarised light which you can see on your computer and TV screens.

The image below shows the polarised light:

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In LCD displays, light emitted from the backlight passes via a vertical polarisation filter after going through the liquid crystal element, this liquid crystal element twists this light wave. The vertically polarised light then turns to a horizontally polarised light. This horizontally polarised light passes via the horizontal polarisation filter allowing the passage of light. Hence the light is visible to us. The voltage we apply to the LCD is applied in such a way that the crystal mechanism of the light is removed and the light acquires a straight pattern. Due to this, the vertically polarised light will come out vertically only, however, the horizontally polarised light will be blocked and we won’t see any light in this case. This is how LCD works on the principle of blocking light.

The image below shows the working of LCD:

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Difference between LCD and LED

Applications of LCD and LED

Here are some applications of LCD:

• Portable electronic games 

• As viewfinders for digital cameras and camcorders

• In video projection systems

• Electronic billboards

• Computer monitors

• Flat-panel televisions

Here are some applications of LED:

• Digital watches

• Digital computers 

• Cell phones

• Bulbs and tubes

• Automotive heat lamps

• Camera flashes 

• Calculators

• Aviation lighting

• Microprocessors 

• Burglar alarms systems

• Traffic signals

• Multiplexers

We know that sound is produced from everything. These days, our activities in fact entire human living is based on sound. We begin our day with an alarm clock followed by many variants of sounds such as music, noise, vehicles, etc. Basically sound is the most essential part of our lives. Every living thing such as the roaring of a lion, crying baby, ultimately when we pour water into a glass we witness the production of sound. Now the question that arose is what is sound? 

 

A sound is a form of energy. The study of sound starts with the properties of sound waves and the types of sound waves. Basically sound is a form of wave or vibration. Human ears can sense the sound waves ranging from 20Hz to 20KHz, known as audible sound range. There are many variants of sounds such as pleasant sound, unpleasant sound, music, noise, soft, loud, etc. In this article, we will study the difference between sound noise music, what is meant by sound, what is the meaning of sound, types of sounds in physics, what is noise, etc.

 

Types of Sound

Before starting with types of sound, let us understand what is sound in physics? Sound waves are longitudinal, mechanical waves. Sound is caused by the back and forth vibration of the particles of the medium through which the sound wave is propagating. The vibrations of the object allow particles in the surrounding medium in vibrational motion, causing the auditory receptors to detect them. This is known as the sound. 

 

Though all the bodies that vibrate in the air can indeed produce sound, we can not hear all of them. Our ears are sensitive to a certain frequency range, depending upon this fact there are only two types of sounds i.e., audible and inaudible sound. The audible sound ranges from 20Hz to 20KHz. The sound waves that are below 20 Hz are known as infrasonic sounds and the sound waves above 20KHz are known as ultrasonic sound. 

 

Audible sound is further classified as pleasant sound and unpleasant sounds. So the pleasant sounds are the group of sounds that makes us feel relaxed like good music such as playing the piano, singing songs etc. At the same time, there are a certain set of sounds that will be unbearable or cause irritation to the hearing body like loud noises such as barking dogs, drilling machines etc. We can say audible sound can be classified into music and noise. 

 

Properties of sound

Sound in itself consists of seven major properties that either make it audible or inaudible, noise or music to the human ears. Different species of animals hear distinct sounds that can be inaudible to humans because of the varying properties of sound. 

Let us take a look at the properties of sound:

1. Frequency: Sound consists of sound waves. These waves are like the waves of water, they go up and down and then up again making a whole cycle. Frequency, or pitch, is the time taken by the soundwaves to complete an entire cycle. It is measured in hertz where one hertz (Hz) is equal to one cycle per second. 

2. Amplitude: The intensity of the soundwave is called its amplitude. The higher the sound waves, the more the intensity and the greater the amplitude. In common man’s language, we call it the volume of the sound. If someone is shouting, it means the sound has high amplitude while whispering can be considered as having low amplitude. 

3. Timbre: Have you ever heard two different instruments that play the same note yet sound so different? It is because they have different tones or timbres. Some frequencies that are lower in pitch are called subtones, while the ones higher in pitch are called overtones. Both of them combined to form ‘harmonics’ and give the sound distinct timbre or tones. 

4. Envelope: Envelope is simply how a sound wave or sound behaves over a particular period. It is also called ADSR, which is short for attack, decay, sustain and release. These are four sub-properties of the envelope. The attack is how fast a sound reaches its highest volume, decay is when it drops before it sustains a constant volume and finally releases into the atmosphere, almost vanishing. 

5. Velocity: The velocity of the sound is the speed at which the soundwaves travel through different mediums. Since, soundwaves use the medium of air to travel, the velocity of the sound can depend on different factors including humidity, temperature and density. 

6. Wavelengths: The difference between consecutive crests of the sound wave is called wavelength. Audible sounds have longer wavelengths than inaudible sounds. 

7. Phase: Phase is described as the difference between amplitude crests and troughs of two sound waves. It is measured in time, degree or distance. Two sound waves that have the same and are perfectly aligned to each other are said to be ‘in phase’; that is their phase difference is zero. It is important to know about the phase of sound to prevent ‘hollow’ sounds. 

 

What is Noise and Types of Noise?

Now, what is noise? So, noise is a type of sound, it is really important to distinguish between what is noise and what is sound. Noise is a type of sound and it can be defined as a type of sound that can be unpleasant, unwanted, annoying or too loud for human ears. 

 

Human ears are highly sensitive and excellent at identifying what is noise. Generally, noise is an annoying tone of sound that causes mild to major discomfort or irritation. These sound vibrations pierce through the background noise that accompanies our lives.

 

When it comes to measuring the different types of noise, we want to replicate how the human ear identifies noise to get an accurate interpretation of its impact. Thus, generally, we use something called the A-weighted frequency, which is much more sensitive between the 500 Hz and 6 kHz range. There are four different types of sound, as listed below:

1. Continuous noise

2. Intermittent noise

3. Impulsive noise

4. Low-frequency noise

Let’s discuss the four types of noise one by one as follows:

1. Continuous Noise:

• As the name suggests it is a type of noise that is produced continuously. 

• The examples of continuous noise are all the machines that run continuously without any breaks such as while riding a car we hear the sound of functioning parts like the engine, in factories large machinery produces continuous noise.

2. Intermittent Noise:

• Intermittent noises are noises
  that are not produced continuously. Intermittent noises are produced continuously but with intermediate breaks.

• The best examples for the intermittent noises are drilling machines, which we might have seen during the destruction or construction of any building we use drilling machines that produce unbearable sound. Another example of intermittent noise is drilling machines used by a carpenter or the dentist. 

3. Impulsive noise:

• It is a type of noise characterized by a noise level of more than 40dB within a half-second with a duration of one second. 

• Impulsive sounds incorporate almost all unwanted, instantaneous sharp sounds.

• Examples of impulsive sounds are bomb explosions, the fringe of weapons, etc.

4. Low-Frequency Noise:

• Low-frequency noise is produced from the objects around us in everyday life. It is one of the difficult types of noise to reduce, and it makes a silent room still register sound levels around 30-40 decibels.

• In an office setting, this noise is produced from a heating or ventilation system. In our house, it will arise from the ticking on a grandfather clock. Generally, we don’t even identify these types of noise unless we direct our attention towards them.

 So, these are the different types of noise and what is the meaning of noise physics.

 

Let us have a look at the difference between sound and noise as listed below:

 

Difference Between Sound and Noise:

 

These are the important differences between sound and noise. Similarly, we can note the difference between the sound and music, music and noise, etc. Learning the difference between these will help us understand the terms in a better way.

 

What is Music?

Music, by its definition, is referred to as vocal and instrumental sounds occurring one after another to create a beautiful symphony of harmony and expression of emotion. A music sheet is the written or printed signs representing these vocal or instrumental sounds.

 

The process of putting sounds and tones in a rhythm, mostly combining them to produce a unified composition is known as making music. Music-making is as much science as it is an art.

 

To create melodious music, you would need a musical instrument or instruments, these instruments create sounds with string, wind, and brass using special kinds of sound waves – known as ‘standing waves.

 

A wave that looks like it isn’t moving is called a standing wave. It only changes amplitude but doesn’t travel through any medium. The standing waves are the result of two other things waves do, reflection and interference.

 

When a sound wave travels through a path, reaches its end and then travels back, reflections occur. That’s what happens when you send a pulse down a rope – it reaches the end, and then comes right back.

 

When we send a continuous wave down the rope, that’s when interference comes into play. The sound wave after reaching the endpoint of the rope is reflected; however, there are more peaks on the path. As the peaks pass each other, they interfere with one another, changing their sizes.

 

Usually, it results in the formation of crests and troughs that are of varying sizes and various distances apart. But at particular frequencies, the reflected waves interfere in such a way that you end up with a wave that seems to stay perfectly still, with only its amplitude changing. That’s a standing wave, and it can be produced by both, the strings and the air in pipes.

 

That is what makes music: standing waves with different frequencies correspond to different musical notes.

 

Did You Know:

• Noise pollution causes hearing loss that is hazardous to human beings. People who are subjected to loud sounds regularly suffer hearing loss. The technical term used for this is Noise-Induced Hearing Loss (NIHL). Dangerous Decibels (an agency) researched the subject and discovered that out of the four million people in the United States who suffer from hearing loss, about 25% of those cases have NIHL.

• About 30 million people in the United States are subjected to hazardous sound levels at their workplace every day, according to a study from 2005.

• In 2015, the Centers for Disease Control and Prevention (CDC), found that mining was the industry with the loudest work environment, followed by manufacturing and construction. About one in eight of the workers in these and similar industries had hearing loss caused by their work environment.