Category: Physics Notes PPT

Styrofoam is closed-cell extruded polystyrene foam and is usually called ‘Blue Board’. It is manufactured as an insulation board and can be used in roofs, walls, and also structures like water barriers and thermal insulation. The material is light blue in colour, but the term is used worldwide to refer to one white material, made of polystyrene (that is expanded). You can also buy this expanded polystyrene as styrofoam sheets or even styrofoam containers. 

What is Styrofoam Made of?

Styrofoam is made of a petroleum-based product that is known as styrene, and it is refined into polystyrene through polymerization followed by the addition of a hydrofluorocarbon agent. This combination lets it extrude and expand until the foam board is formed.

This polystyrene foam is used for craft applications and is known for the hard sound that it makes when it has been cut or a part of it is torn off, and the material is also rather rough. It is also found to be moderately soluble in cyanoacrylate, many organic solutions, and even in the solvents and propellants of spray paint.

Dow’s Chemical Physics Lab, which was led by Ray McIntire, found a method through which to make foamed polystyrene in the 1940s. They actually rediscovered a method that was originally used by Carl Georg Munters and managed to get an exclusive license to his patent in America. Dow adopted the method used by Munters to make significant amounts of extruded polystyrene as a moisture-resistant closed-cell foam. They also filed a patent on this specific adaptation in the year 1947.

Uses of Styrofoam

Styrofoam is made of 98% air, and this makes it buoyant, lightweight, and extremely useful. Dow produced and patented styrofoam that is used for building materials, including pipe insulation and types of building insulating sheathing. The R-value of this materials’ insulation is said to be five per inch.

Styrofoam can also be used under structures like roads in order to avoid the soil disturbances that occur in the winters due to freezing and thawing. It can also be used as a structural insulated panel for the usage of craft products and even by florists. Please note that styrofoam for craft application is usually found in green and white colour, but the Dow Insulation one is blue in colour. The craft made of this material also includes styrofoam sculptures.

Non-Biodegradable Pollutant

The downside to this material, despite its great usefulness, is that it is not known how long it takes for this material to biodegrade. Some estimate that it can take up to 500 years, and this is with the limited options that there are for recycling it.

Styrofoam, when used with food products and heated, will release into the food certain toxic chemicals that will cause contamination and can be disastrous to human health. It even creates harmful air pollutants when it is exposed to sunlight, and it can contaminate landfills in which it is discarded and even cause depletion of the ozone layer. This means that Styrofoam is a type of waste that is harmful to the environment. This is having a large and adverse impact on the ecological system of the planet on various levels.

Landfills

Styrofoam poses a threat to the environment and just in the U.S landfills, there are about 1,369 tons of it being buried. Landfills are therefore filling up quickly with it, and this is a material that takes up more space. In fact, in landfill space across the world, styrofoam takes up 25-30% of the space. In 2006, according to an environmental group, about 135 tons of polystyrene waste was being disposed of in Hong Kong landfills every day. 

Many countries have therefore implemented a ban on its commercial usage for its environmental impact, and this includes certain places in the USA, Canada, France, Philippines, Taiwan, etc.

Impact on Animals

Styrofoam can cause a great deal of harm to all the animals that consume food from landfills. Since these products can be broken apart into smaller pieces very easily, it becomes a choking hazard to these creatures.

Statistics.

Styrofoam is said to be unsinkable and has the ability to maintain its form due to the air present in its structure. As mentioned, it does not even break down or degrade over time. It can only be incinerated at temperatures that are extremely high and will only release carbon and a small amount of water as byproducts. However, if a specialised incinerator is not used and it is burned in a normal fire, it will let out pollutants like carbon monoxide.

It was reported that in the year 1986, the fifth largest producers of toxic waste were the Styrofoam manufacturers. There are more than 90,000 workers that get exposed to the effects of styrene (which is what polystyrene is made of), every single year in companies and industries that work with fibreglass and rubber.

The International Agency for Research on Cancer and the Environmental Protection Agency even classify it as a possible human carcinogen. Exposure to styrene includes gastrointestinal problems and irritation to the respiratory tract, eyes, and skin.

Recycling

While the scope for recycling styrofoam is limited, it is still important to do this as much as possible. There are businesses that collect this material for reuse and recycling. The other option to avoid the problems this material creates is to go for eco-friendly products that could be an alternative. Even food and packaging industries use alternatives, and this can help conserve the landfills and reduce pollution.

When does force take place? If two bodies are in physical contact, then we notice that they apply forces on each other. Well, what’s in it for tension? Have you ever pulled something up or toward you using a rope? If you do, you are putting the rope in tension.

This article will explain how all of these processes are executed? When a body is in contact with a rope, string, cable, or spring, all of these objects are going through tension. We can also calculate the tension in string formula with ease. 

Dimensional Formula of Tension

Tension is a type of force that acts along the length of the medium such as rope or string. A force is necessary to put these objects under tension. Tension is also named something exciting, i.e. action-reaction pair.

(Image to be added soon)

The Tension Dimensional Formula = [M1 L1 T-2]

Tension is nothing, but it’s a force that has got another improved name. Tension acts at both the end of the string (from the above picture). The tension force is available on each point of the string.

Tension Force Formula

You can calculate the tension formula on a body by the summation of the product of mass and gravitational force along with the product of mass and acceleration.

So, the tension equation is equal to T = mg + ma

Tension Force Examples

Let’s solve a question. 

Q. Find the tension on a string if it is dangled with a brick of 10 kg. Acceleration is 3 m/s2 in the upward direction.

Ans: Data are given, m = mass of the brick = 10 Kg

When the brick is getting an upward acceleration, the Tension Formula Physics is expressed as

T (Tension in A String Formula) = mg + ma 

= 10 × 9.8 + 10 × 3 = 128 N

Surface Tension Equation

Surface tension is defined as a phenomenon that happens when a phase has made the interaction with the surface of a liquid. The other phase can also be a liquid. Liquids tend to occupy the least surface area. They behave like elastic sheets.

The formula for the surface tension is:

ℽ = ½ . F/L 

Here, T = Surface Tension of the liquid

L = length on which the force exerts

F = force per unit length

Tension Formula Pulley

(Image to be added soon)

If the wedge of mass (m) is heaved upwards by two forces of F and T, then the mg will be alike the sum of F and T.  So,

2F = mg 

or F = mg / 2

We know that there are various methods that can be taken to get a Thermodynamic system from its beginning state to its ultimate state. We’ll talk about those Thermodynamic processes in this article. We’ll look at what a quasi-static process is first. State variables are defined only when the Thermodynamic system is in equilibrium with its surroundings, as previously explained. A quasi-static process is one in which the system is in Thermodynamic equilibrium with its surroundings at all times.

In a refrigerator, how does food stay cold and fresh? Have you ever noticed that even when a refrigerator’s entire inside compartment is chilly, the outside or back of the refrigerator is warm? Here, the refrigerator extracts heat from its interior and transmits it to the surrounding area. This is why a refrigerator’s back is warm. Thermodynamic processes are the movement of heat energy within or between systems.

A Thermodynamic system is a specific space or macroscopic region in the universe, whose state can be expressed in terms of pressure, temperature, and volume, and in which one or more than one Thermodynamic process occurs. Anything external to this Thermodynamic system represents the surroundings and is separated from the system by a boundary. The surroundings, system, and the boundary, together constitute the universe. Types of systems in Thermodynamics are as follows:

• Open System: It allows energy as well as mass to flow in and out of it.

• Closed System: It only allows energy (work and heat) to be transferred across its boundary.

• Isolated System: Neither mass nor energy is allowed to interact with it.

In the winter, rubbing your palms together makes you feel warmer. Because touching our palms produces heat, this happens. The heat of the steam is also used in steam engines to move the pistons, which causes the train wheels to rotate. But what is the actual procedure here? This is related to a phenomenon known as ‘Thermodynamics.’

The study of the relationship between heat, work, temperature, and energy is known as Thermodynamics. Thermodynamics is concerned with the movement of energy from one location to another and from one form to another in its broadest definition. The essential concept is that heat is a sort of energy that correlates to a specified quantity of mechanical labor.

The heat was not formally recognized as a form of energy until around 1798, when Count Rumford (Sir Benjamin Thompson), a British military engineer, discovered that infinite amounts of heat might be produced while boring cannon barrels, and that the quantity of heat produced is proportionate to the amount of work done in spinning a blunt boring instrument. The foundation of Thermodynamics is Rumford’s observation of the relation between heat created and work done. Carnot’s research focused on the limits to the maximum amount of work that a steam engine can produce when using a high-temperature heat transfer as its driving force. Rudolf Clausius, a German mathematician, and physicist, refined these ideas into the first and second laws of Thermodynamics later that century.

Types of Thermodynamic Processes

The state of a given Thermodynamic system can be expressed by various parameters such as pressure (P), temperature (T), volume (V), and internal energy (U). If any two parameters are fixed, say, pressure (P) and volume (V) of a fixed mass of gas, then the temperature (T) of the gas will be automatically fixed according to the equation PV =RT. No change can be made to T without altering P and V.

The state of a system can be changed by different processes. In Thermodynamics, types of processes include:

• Isobaric process in which the pressure (P) is kept constant (ΔP =0).

• Isochoric process in which the volume (V) is kept constant (ΔV =0).

• Isothermal process in which the temperature (T) is kept constant (ΔT =0).

• Adiabatic process in which the heat transfer is zero (Q=0).

Thermodynamic process notes have been discussed later.

Work in Thermodynamic Processes

When the volume (V) of a system alters, it is said that pressure-volume work has occurred. A Thermodynamic process occurring in a closed system in such a way that the rate of volume change is slow enough for the pressure (P) to remain constant and uniform throughout the system, is a quasi-static process. In this case, work (W) is represented as:

δW = PdV, where δW is the infinitesimal work increment by the system, and dV is the infinitesimal volume increment.

Also, W = [int] PdV, where W is the work the system does during the entire reversible process.

Isobaric Process

Since the pressure (P) is constant in this process, the volume of the system changes. The work (W) done can be calculated as W = P (Vfinal – Vinitial).

If ΔV is positive (expansion), the work done is positive. For negative ΔV (contraction), the work done is negative.

Isochoric Process

The volume remains constant in an isochoric process. Therefore, the system does not do any work (since ΔV = 0, PΔV or W is also zero). Such a process in which there is no change in volume can be achieved by placing a Thermodynamic system in a closed container that neither contracts nor expands. Thus, from the first law of Thermodynamics (Q = ΔU + W), the change in internal energy becomes equal to the heat transferred (ΔU = Q) for an isochoric process.

Isothermal Process

The temperature of the system remains constant in an isothermal process. We know,

W = [int] PdV

From Gas Law, 

PV = nRT

P = nRT/V. Using the value of P in the work equation:

W = nRT VB [int]VA (dV/V)

W = nRT ln (VB/VA)

If VB is higher than VA, the work done will be positive, or else negative.

Since internal energy is temperature-dependent, ΔU = 0 because the temperature is constant, and thus, from the first law of Thermodynamics (Q = ΔU + W), we will get Q = W.

Adiabatic Process

No heat is exchanged with the system in an adiabatic process (Q = 0). Its mathematical representation is:

 PVƔ = K (constant).

Also, W =  [int] PdV. Substituting the value of P in the work equation:

W = K Vf [int]Vi (dV/VƔ)

W = K [(Vf1-Ɣ – Vi1-Ɣ)/ 1-Ɣ]

Since Q = 0 for an adiabatic process, from the first law of Thermodynamics (Q = ΔU + W), we will get ΔU = -W. Thus, the internal energy will increase if the work done is negative and vice versa.

To convert the given galvanometer into an ammeter of desired range and to verify the same we need to see the article in depth.

A Weston type galvanometer that is said to be an ammeter of 0-3 A. range and a battery which is of two cells or battery eliminator that is of two which is 10,000 Ω and 200 Ω resistance boxes there are two one way keys and a rheostat then the connecting wires and a piece of sandpaper.

The materials required

• A galvanometer of Weston type

• an Ammeter of the range 0-3 A

• A Battery with two cells

• And two resistance boxes that are of 10,000Ω and 200Ω respectively

• Then Two one way keys

•  Rheostat

• Then the connecting wires

• The piece of sandpaper

What is a Galvanometer 

We can also say that a galvanometer works as an actuator by producing a rotary deflection of a pointer that is in response to electric current which is flowing through a coil in a constant magnetic field. We can say that early galvanometers were not calibrated but now as we can see that the improved devices were used as measuring instruments known as the ammeters which in this article we will learn to measure the current flowing through an electric circuit.

The term that is galvanometers is developed from the observation that the needle of a magnetic compass which is said to be deflected near a wire that has electric current flowing through it was first described by Sir Hans Christian Ørsted in 1820. They were the first instruments that were used to detect and measure the very small amounts of electric currents. Sir André-Marie Ampère who gave mathematical expression to Ørsted’s discovery and named the instrument after the Italian researcher who was Luigi Galvani who discovered the principle of the frog galvanoscope in 1719 – that electric current would make the legs of a dead frog jerk at that time.

What is an Ammeter 

An ammeter that is from an ampere meter is said to be a measuring instrument used to measure the current in a circuit. Electric currents which are generally measured in amperes that are denoted as A hence the name is an ammeter. The ammeter is usually said to be connected in series with the circuit in which the current is to be measured. An ammeter usually has a resistance which is low resistance so that it does not cause a significant drop of the voltage in the circuit being measured.

We can say that early meters were laboratory instruments that relied on the magnetic field of Earth’s field for operation. By the late 19th century there were improved instruments which were designed which could be mounted in any position and allowed accurate measurements in the electric system of power. It is said to be generally represented by the letter denoted by  ‘A’ in a circuit.

The majority of ammeters that are said to be either connected in series or with the circuit which is carrying the current to be measured that is for small fractional amperes or have their shunt resistors that are connected similarly in series. In either case, we can say that the current generally passes through the meter or we can say mostly through its shunt. Here we will say that the ordinary Weston-type meter movements can measure only milliamperes at most because the springs and practical coils can carry only limited currents. To measure the current which is larger a resistor known as a shunt is placed in parallel with the meter. 

Conversion of Galvanometer into Ammeter

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The Procedure 

1. The count of the total number which is of divisions on either side of zero of the galvanometer scale. Let it be denoted by letter that is n.

2. Then we need to calculate the current that is Ig for full-scale deflection that is  Ig = nk.

3. Now we will calculate the value that is of resistance of shunt for conversion into ammeter that is said to be  using the formula:

S = [frac{I_{g}.G}{I-I_{g}}]

Where letter that is I is the range of conversion.

The value which is of shunt resistance that is said to be denoted by letter S is usually very small and a resistance box of that range is not available. Such small resistances which are obtained by taking wires that are made of copper and constantan, manganin, eureka, etc., of a suitable diameter and length.

4. Then we need to cut a length of the wire that is 2 cm more than the calculated value of the l.  We then need to mark two points on the wire that is one cm away from each end. Then we will connect this wire to the two terminals of the galvanometer such that the points which are marked are just outside the terminal screws. Then make the electric connections that are as shown in the circuit diagram.

5. Then we need to insert the key and adjust the rheostat that is so that the galvanometer shows nearly maximum deflection.

6. We need to note the reading which is on the galvanometer scale and also corresponding reading on the ammeter.

7. Then we need to record our observations.

Result of the Experiment 

As the difference in the measured and actual value of currents that are as recorded in observation is very small that is the conversion is perfect.

Lamina in Physics

Lamina in Latin is another word for leaf.

In physics, a lamina is a two-dimensional planar closed surface which has a mass and a surface density (its surface density is calculated in the units of mass per square area).

If the object has uniform density, the center of mass of a lamina is called its geometric center.

This geometric center is also called the geometric centroid of the object.

If you look at Fig.1, the center of mass of the lamina is P.

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We can see that the center of mass or the geometric centroid lies in the object itself.

What is a Screw Gauge?

Screw gauge is a form of the caliper that is used for measuring the thickness of thin glass and the diameter of a wire, plastic, or small dimensions of the objects like the sphere with an accuracy of 0.01 mm. 

It was invented by William Gascoigne in the 17th Century, as an enhancement of the Vernier.

They are extensively utilized in the engineering field for obtaining accurate measurements.

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The Principle of a Screw Gauge

The screw gauge works on the principle of a screw in a nut and hence it is called a screw gauge.

A screw gauge works on the simple principle of converting small distances into larger ones by measuring the rotation of the screw. 

This “screw” principle facilitates the reading of smaller distances on a scale after amplifying them. To simplify it further, let’s take a normal screw with threads.

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To determine the volume of an irregular lamina using screw gauge

Irregular Lamina

An irregular lamina is an irregular polygon that doesn’t have a proper shape, and its thickness is negligible as compared to its length and breadth.

Its volume is calculated by the formula:

Volume = Area * Thickness

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The thickness of a lamina can be calculated by using the screw gauge while its surface area is measured using a graph paper.

Aim

To determine the volume of an irregular lamina

Materials Required:

1. Screw gauge

2. Irregular lamina of uniform thickness

3. A centimeter graph paper

4. A pencil

Theory

Screw gauge is also called the micrometer screw.

It uses a screw to amplify a very small movement so that it can be easily read.

It usually measures the diameters at 0.001 cm.

It consists of a U-shaped frame fitted with a screwed spindle that is attached to a thimble. 

Parallel to the axis of the thimble, a scale graduated in mm is inscribed. This is known as the pitch scale.

The head of the screw consists of a ratchet that prevents undue tightening of the screw, and on the thimble, there is a circular scale known as the head scale that is divided into 50 to 100 equal parts. 

A screw gauge works on the principle of the nut in a screw.

So, by rotating the screw head, we get the linear movement of the main scale which is a linear movement. 

This linear movement is used to calculate the diameter of a wire or thickness of the metal plate.

This is how we can determine the volume of an irregular shaped lamina.

Here, we will talk about two parameters used in the screw gauge, that are:

1. The Pitch of a Screw Gauge

It is defined as the distance moved by the spindle per revolution that is measured by moving the head scale over the pitch scale to complete one full rotation. Its formula is given by:

Formula = Distance traveled by the screw/number of rotations made by the spindle

2. The Formula for Least Count of the Screw Gauge

The least count (LC) of the screw is defined as the distance traversed by the tip of the screw when turned through a division of the head scale.

Formula = Pitch of the screw gauge/total number of divisions on the circular scale.    

Procedure to Determine the Volume of an Irregular Lamina

1. To calculate the thickness of an irregular lamina, use the procedure of finding the thickness of a wire.

2. To find the area of the lamina

Take a graph paper and consider the area of the square as 1 cm².

Place the lamina on a centimeter graph and mark its boundary using a pencil.

Count the number of squares enclosed on graph paper by the boundary of the lamina.

Let’s say, the counted squares are ‘n’ in total.

When multiplied by 1 cm², the area of the lamina becomes n cm².

Observations

Use the formula:

Area of the lamina = ____ cm² &  the thickness = ____ cm.

Result 

The volume of the lamina = ____ cm³.

We all travel from place to place for employment, school, and to see our families, among other things. Every morning, you stand at your bus stop, anticipating the arrival of your school bus. Your school bus transports you to school. 

Whenever we have employment, we go from one location to another utilising various modes of transportation. So, let’s read about travelling and communication in our daily lives.

Travel Meaning

The term “travel” refers to the act of moving from one area to another. We travel for a variety of reasons. Depending on the objective of our trip, we go alone, in groups, with our family, or with our classmates. There are numerous purposes such as going to school, college, and so on. 

We also travel to distant cities to visit family, spend vacations, and go on school excursions. We either travel alone, such as when our parents go to their offices, or we go with our families, such as when we visit relatives or attend family festivities.

Ways to Travel

There are numerous ways to travel and some of which are explained below;

• Travel by Road: Different towns and cities are connected via roads. Buses, motorbikes, cars, trucks, scooters, and other road vehicles are the most frequent modes of travel.

• Travel by Rail: Rail transport encompasses all modes of transportation that use rails or tracks. This includes both passenger and freight trains. When compared to vehicle travel, rail transports more people or products.

• Travel by Air: Travel by air includes travel by aeroplane, parachute and helicopter. It is the fastest mode of travel that is able to connect all the major cities. Air travel allows you to go to another nation in a matter of hours or days.

• Travel by Water: Travelling by boat, ship, or submarine is an example of water travel. Streamers and boats float down major rivers, while ships navigate the oceans and seas, transporting passengers and commodities across continents.

What is Communication?

We communicate with a significant number of people every day. Consider what would happen if no one communicated with one another. We would not be able to communicate our thoughts, ideas, and emotions. Therefore, communication is an integral component of our lives.

Communication Types

Mainly there are two types of communication which are explained below as;

• Verbal Communication: Words are used to communicate our thoughts via verbal conversation. Written and oral communication are the two basic types of verbal communication. Written communication comprises handwritten letters, papers, and so on, whereas oral communication includes speeches, lectures, and voice chats, among other things.

• Non-verbal Communication: The words aren’t included. It’s done with facial expressions, body gestures, signs, drawings, graphic designs, etc. Waving a hand, pointing a finger, and smiling are some of its examples.

Communication Methods

The main modes of communication are postal communication, mass communication and telecommunication and these are explained below.

• Postal Communication: It involves letter writing. Though writing a letter is not as popular as it once was, it is one of the oldest means of communication. We compose a letter and include the address, then place it in a neighbouring mailbox. Later, a postal worker will collect the letters, sort them, and deliver them to their corresponding addresses.

• Telecommunication: Telecommunication refers to long-distance communication. Telegrams, cell phones, and landlines are all examples of telecommunications.

• Mass Communication: The transmission or exchange of information to a large number of individuals at the same time is referred to as mass communication. Newspapers, magazines, radio, television, and cinema are examples of numerous forms of mass communication.

Importance of Travel and Communication

The utilisation of natural resources, the mobility of skilled labour, and a rise in agricultural and industrial production are all promoted by travel and communication networks. People in rural regions benefit from travel and communication services since they assist in establishing work prospects.

Solved Questions

1. What is the reason behind travelling?

Ans: We travel only when we have to go to work or to a school for studying or going on vacation. The means of transportation totally depends on the distance that we have to travel. Suppose if we have to travel from one city to another then we choose to prefer bus travelling and if we have to from one country to another then we have to travel by air.

2. What are the various ways through which we can communicate with each other?

Ans: We can communicate in two ways i.e, verbally and non-verbally. In verbal mode, we can express our feelings and thoughts by writing a letter and in the non-verbal mode, we can express our feelings through body gestures and facial expressions.

3. What is the importance of communication?

Ans: It is necessary to communicate in order to express oneself. It also meets one’s requirements. Effective communication is necessary for growth in life. Effective communication skills may smooth your path and improve your interactions with people in your daily life by allowing you to understand and be understood by others.

Fun Facts

• Do you know that in ancient times, horses and oxen were used for travelling purposes.

• In ancient times, the birds were used for communication purposes like sending written messages from one place to another.

Summary

In this article, we have discussed why we need to travel and also about the various ways of travelling. We have mentioned the need for communication and why it is necessary to communicate. The various modes of communication such as verbal and non-verbal modes of communication are also discussed.

Learning By Doing

• Think about which type of communication mode is used through television.

• For travelling between two towns, which mode of travel would you prefer?< /p>