Category: Physics Notes PPT

Our solar system has a star at the center, known as the Sun. This star emanates a rigorous stream of charged particles, forming an interplanetary space. 

A heliosphere is nothing more than an interplanetary space (region of space) created by the Sun and vastly surrounds the same. 

Belonging to the astronomical category, the noun Heliosphere (pronounced as hee-lee-uh-sfeer) is a region neighbouring the Sun, over which the effect of solar wind is significantly high. 

History and Formation

The word heliosphere is derived from the Greek word helios, meaning the Sun. 

The formation process of the sun heliosphere is not complex but definitely takes over a millennia. 

Initial speculations about the existence and nature of the solar system heliosphere, begin in and around 1955 by a physicist, Leverett Davis. 

Early credit for the existence of the heliosphere was attributed to the origin of cosmic rays. Back in 1955, ‘solar wind’ was called the solar corpuscular radiation and it was known to be an essential element in the mere presence of the sun’s heliosphere. 

An explanation was given, which if translated in simpler terms would mean that the solar corpuscular radiation whisks a spherical bubble that continues to expand over the years, circumferencing the solar system. Apparently, that ‘spherical bubble’ is the heliosphere.

Conditions regarding the exception of this solar process are also stated, the most acceptable of them being: the continuous expansion of the solar system heliosphere must stop if there is a pressure created in the interstellar medium.

NASA, also explains the formation of the heliosphere as the result of the magnetic flux created by the solar wind, but it adds a few more reasons as to why this must be so. After the sun sends out the solar wind (in the form of constant flow of charged particles), it (supposedly) travels past all the 8 planets of our solar system to some three times the distance to Pluto, after which it eventually gets obstructed by an interstellar medium, a process scientifically known as the termination shock. 

Structure of Heliosphere

Heliospheric research has been in action for the past few decades. Attempts to provide information about the exact structure of the solar system heliosphere is made by numerous researchers, physicists, and scientific organizations. 

Not surprisingly, the heliosphere is not actually a perfect sphere in its perception. The shape and size of the sun heliosphere are fluid, mainly because of the equally fluid composition and nature of the solar wind and the interstellar medium (ISM). 

Broadly, the shape and size of the heliosphere are dependent upon 3 individual and interdependent solar phenomena, i.e, the comprehensive motion of the heliosphere and the Sun, the solar wind, and the interstellar medium (ISM), the last two being fluid, as mentioned earlier. 

If you’re familiar with the shape of a comet, then assuming the shape of a heliosphere will not be as tough. The motion of the heliosphere through the fluxional medium of the ISM results in the same. 

Some Components that Complete the Structure of a Heliosphere are:

• Heliospheric Current Sheet: The rotating magnetic field of the Sun produces a ripple in the heliosphere, known as the heliospheric current sheet. Said to resemble a Ballerina’s skirt, the heliospheric current sheet is by far the largest structure in the solar system. 

• Heliosheath: Afar the termination shock, there lies a region of the heliosphere, known as the heliosheath. Lying approximately 80 to 100 AU from the Sun, the heliosheath is shaped like a coma. 

• Heliopause: This is the region, where the strength of the solar wind declines dramatically, making it difficult for the wind to fight and push back the winds of the surrounding stars (stellar winds). It is a theoretical boundary where the ISM meets the solar wind to hamper its speed. 

• Heliotail: As the name suggests, heliotail is the tail of the heliosphere, and can be understood as a region where the solar wind marks its exit from the heliosphere, attributing to the charge exchange. NASA’s IBEX recently found the shape of heliotail similar to that of a four-leaf clover. 

Heliosphere Composition 

The boundaries of the heliosphere are thought to extend about 9-10 billion miles from the Sun afar the orbit of Pluto. In this giant spherical bubble, the solar wind is the main component within the mixture of electrically neutral gas, ionized gas, and interstellar dust that are widely known to form our solar system’s local galactic environment.

The Heliosphere is a beautiful creation of nature and observing it might be one of the greatest gifts for space-lovers. In doing so, interplanetary spacecraft such as Pioneer 10, Pioneer 11, and New Horizons have been successful in getting a step closer to observe the phenomena and are eventually hoping to pass through the heliopause. 

Importance of Heliosphere

Known as the ‘protective bubble’ of the earth, the heliosphere is primarily important because of its role in minimizing the harmful effects of external radiations such as high-intensity gamma rays, which are thought to deplete the integral composition of our solar system. 

• Distance: The solar system heliosphere is at a distance of about 123 AU (11 billion miles) from the Sun. 

• Location: In the Milky Way Galaxy, a region known as the Orion Arm comprises the sun heliosphere. 

• Edge: The outermost edge, heliopause, separates the hot solar plasma from the cooler interstellar plasma. 

Given the significance and major properties of the heliosphere, more research in the concerned area is demanded to stir up the contemporary knowledge of this universal phenomenon. 

This is an experiment in which students will be able to observe a balloon which does not explode by the flamme. They will be able to defy logic by putting flame to the balloon, and the balloon does not pop. The actual magic is of water in the experiment as water has the ability to conduct heat. It has high heat capacity. Water takes a lot of energy and heat to change the temperature by 1 degree celsius. This experiment’s objective is to describe the relation between thermal heating or cooling and water’s heat capacity.  And compare the water’s and air’s thermal conductivity. 

Balloon Experiment

This experiment includes the following materials listed below:

In this experiment we have to blow a balloon and tie it up. Then we have to light a candle and place it on a candle holder so that the candle dosen falls and we have to keep it in the center of the table, so that viewers can see the experiment nicely. Put on the safety glasses for personal safety while the experiment is going on. Hold the balloon above the flame at least 30 to 50 cm. Slowly start moving the balloon closer to the flame until it pops. One thing should be noted that the balloon should not touch the flame, it should just be brought closer to the flame. Note the notations and time.

Now take another balloon and add at least 60ml of water inside it and then blow it up to the same size as the first one. As done earlier the same set up should be made and the same way a second balloon should also be brought near the flame. This time ciwers will notice that the balloon does not pop. it will simply leave a mark at the bottom of the balloon.

[Image to be added Soon]

Now the question arises why does the balloon which was not filled with water breaks?

The answer to it lies in the experiment itself. The flamme is a substance that heats anything near it and this quality of heat can change the shape and size of the matter. It heats the latex of both the balloons but the rubber of the first balloon which does not contain water becomes very hot and it becomes very weak to resist the pressure exerted by the flame to the balloon. The second balloon which contained water did not break it is because when the filled water inside the balloon is brought near the flame the water starts absorbing most of the heat which comes from the flame. And so the rubber of the balloon does not become hot.  

It does not get weak nor does it break. Water is known as a good absorber of the heat, and it takes a lot of heat to change the temperature of the water. To raise the temperature of 1 gram of water by 1 degree celsius it takes a lot of heat it takes nearly the same amount of heat to heat 1 gram of iron.

Fireproof Balloons Experiment Application

We have already discussed how plays an important role in this experiment and so doest it plays in many other things. This experiment explains a lot of things like the water takes a lot of heat to get heated nearly it takes the same heat of heating an iron, and water also releases a lot of heat while being cool or coming back to its temperature. This is why a tea kettle takes a lot of time in boiling. Water cools also very late this is why the areas which are near seas or oceans or large water bodies do not get cold in the winter seasons as the area further inlands.

It’s a vulnerable process of using heat control. The firefighters currently use the fireproof absorbent polymer foams which helps in protecting homes from being consumed by the forest fires or dangerous fires. There is another foam which is known as the water absorbing polymer foam which is just like a baby diaper and is similar to the fireproof absorbent polymer. These foams are applied as shaving cream towards the outside of the house or building which has caught fire.

As the fire grows closer and closer to the house these water filled foams start absorbing the heat energy from the burning fire, whereas on the other side there are firefighters which start to fight with the fire which takes a little time to extinguish it making large amounts of losses. Our body is also made up of 70% of water which balances our body. To control heat our body uses water. When we start to exercise our body starts producing sweets and it does so to regulate the temperature of the body, because of this we don’t get overheated. As our sweets start evaporating it takes away all the heat energy along with it leaving cooler skin behind which makes us feel cool.

There are several ways of producing electricity, we use different types of power plants depending upon the availability of the source. For example, we have thermal power plants, we have tidal power plants, etc. One of the most widely utilized power plants is the hydroelectric power plants.

Hydroelectric power plants are designed for producing electricity with the help of the flow of water also known as hydro energy. We know that 75% of the land is covered with water. Also, water is the primary energy source available.

Hydro Power Plant

While learning about hydraulic machines, one of the most important hydraulic machines to be studied is the Hydroelectric power plant which generates hydroelectric energy or hydropower energy.  

Components of Hydroelectric Power Plant

The hydroelectric power plant utilizes the kinetic energy developed by gravitational potential energy due to falling water. The main part of the hydroelectric power plant is a water turbine generator.

The important parts of the hydroelectric power plant are:

1. The reservoir: It is the part where the water will be stored.

2. The turbine: The equipment used to generate kinetic energy as soon as the waterfall from a height.

3. Generator: It will generate electricity by converting mechanical energy into electrical energy.

4. Powerhouse: It will store all the electricity generated and then it will distribute through transmission lines or the power lines.

Working of Hydroelectric Power Plant

• The potential energy stored in the water of the reservoir stored at a higher level will release as kinetic energy as it falls to the lower level. 

• Water from the reservoir will be made to fall on the turbine in such a way that the force due to the waterfall will result in rotating the turbine. 

• The turbine is further connected to the generator, then the generator will generate electricity. The electricity produced is also known as the hydroelectric current or hydropower.

This is how hydroelectric power plants work and hence produce electricity which is further transmitted through transmission lines as per the need.

Did you know?

• The Three Gorges Dam is the biggest hydroelectric power plant available in the entire world.

• The Three Gorges Dam, a hydroelectric project located in China. It has the capacity of generating 22,500MW (Megawatt) power. 

• Tehri hydroelectric complex is the largest hydroelectric power plant in India, it consists of the potential of generating 2400MW power or hydroelectricity. 

• The Koyna hydroelectric project is the second-largest power station with a capacity of generating 1900Mw hydropower. Koyna has 4 hydroelectric dams with a great hydroelectric generator.

On passing a changing current through a closed-current carrying conductor or an inductor, a magnetic field generates around it. 

In simple terms, this changing current produces an additional current, i.e., an induced current. 

This induced current creates an EMF that opposes the further change in the current.  This opposing ability is what we call inductance. 

When the inductance happens within the same coil, it is self-inductance. 

However, if the current flow in the primary coil shows the inductance effect in the secondary coil, we call it mutual inductance.

This page discusses in-depth the types of inductance with their uses.

Electric Induction

When a current establishes in a closed conducting loop, it generates a magnetic field. 

Further, this magnetic field generates flux (magnetic induction) in an area of the closed-loop. 

So, when the current varies with time, the flux via the loop also changes. 

Furthermore, this variation generates an induced EMF in the loop. We call this phenomenon self-induction.

Here, we note that the magnetic field at any point varies directly with the current. The magnetic flux in an enclosed area of the conductor is given as;                 

Φ  ∝ i  =>   Φ = L i

So, the more is the change in the current, the more in the flux generation. 

Therefore, removing the sign of proportionality constant, we get “L,” which is the coefficient of self-inductance or simply self-inductance of the loop.                        

The inductance in the coil (Fig.1) depends on the following parameters:

1. The number of turns, 

2. Area of cross-section, and 

3. The nature of the material of the core on which the coil is wrapped.

Inductance Definition

If i =1,  

Φ = L x i  

Or

L =    Φ

We say that the coefficient of self-inductance is numerically equal to the amount of magnetic flux associated with the coil when unit current flows through it.

From Faraday’s law of induction, any change in the magnetic field induces an emf, which is given by,

E =  –  dΦ (t) / dt  

= – L di / dt

The negative sign shows that the changing current induces a voltage in the conductor

The induced voltage produced in the same direction opposes any increase or decrease in the electric current (Lenz’s law). We also call this phenomenon the back EMF.

Types of Inductors

Induction is a magic that a closed-current loop or an ability acquires. The types of inductance are:

• Self inductance

• Mutual inductance

Self Inductance

The concept of self induction lie hereunder:

Let’s consider a circular loop in which changing current produces a magnetic field (B). 

Here, we can determine the direction of the magnetic field by curling the fingers of our right hand in the direction of B, pointing inwards. We indicate the inward direction by making cross marks, as shown in the diagram below:

                           

Furthermore, on increasing the current, the magnetic field lines also increase. 

This means B α i

Due to the increase in B, flux (ΦB) also increases. 

Here, we notice that when the flux increases, by Faraday’s law of electromagnetic induction, an EMF also induces in this induction coil.

By Lenz’s law, we can state the above principle in the following manner:

Firstly, we call this induced EMF the potential difference (push) between the two points in the coil because of which an induced current generates. 

Secondly, this induced current decreases the primary current. Its direction points outward, i.e., opposite to the direction of B.

Therefore, an induced current opposes the flux (ΦB) or the magnetic field lines because of which it was generated.

Since this is happening inside the coil itself, we call it self-inductance.

Mutual Inductance

To understand what mutual induction is, let us take two distinct coils P and S and set them side-by-side.                                                       

Connect P to the switch, and S to a galvanometer.

    

                            

Also, on supplying a varying current across P, a current induces in the coil S.

It happens because a varying current in P generates varying magnetic field lines that cross both the coils.

Hence, the increasing current in P increases the magnetic field lines in S, i.e., the flux. 

Accordingly, when ΦB increases, an induced EMF generates in the coil because of which an induced current starts flowing in it. 

      

                           

Therefore, the galvanometer (connected to S) shows a deflection.

To determine the direction of the magnetic field lines, we curl/curve our right-hand fingers around the wire in the following manner:

      

                                

Here, the direction in which the thumb points is the magnetic field’s direction.

It means that the magnetic field lines lie parallel to the direction of the current. 

Additionally, these lines change (because of the changing current), the flux in S changes because of which an induced emf and the induced current generates in it.

Uses of Inductors

Inductors have applications in various electrical transmissions. Besides this, the uses of inductors are:

1. Transformers (Step-up and Step-down transformers)

2. Tuning circuits

3. Sensors

4. Store energy in a device

5. Induction motors

6. Filters

7. Chokes

8. Ferrite beads

9. As relays

Ionizing radiation is a type of energy released by atoms that travel in the form of particles (alpha, beta, or neutrons) or electromagnetic waves (X-rays or gamma rays). The energy emitted is in the form of ionizing radiation. Radioactivity is the spontaneous emission of radiation in the form of high energy photons resulting from a nuclear reaction. It is a random process that occurs at the level of individual atoms. Radioactive substances like thorium, uranium, and radium produce radiation and they also produce a lot of energy. They all can easily knock electrons out of atoms and form charged particles.

Ionizing Radiation Definition

Ionizing radiation is radiation with great energy so that during an interaction with the atom, it can remove tightly bound electrons from the orbit of an atom, causing the atom to be changed from their neutral state. Ionizing radiation occurs in two forms- waves or particles. It is made up of ions, atoms, or energetic subatomic particles moving at high speeds and electromagnetic waves on the high-energy end of the electromagnetic spectrum.

X-rays, gamma rays and the ultraviolet part of the electromagnetic spectrum. It has more energy than non-ionizing radiation, enough to cause chemical changes by breaking bonds. 

There are 3 main types of ionizing radiation:

• Alpha particles 

• Beta particles

• Gamma rays 

Alpha Particles

Alpha particles are particulate radiations with hugely ionizing form. Alpha particles are slower and heavier than x-rays and gamma rays. These particles become dangerous when they are inhaled. Radon is odorless, colorless, and tasteless gas which comes from the decay of the element radium. The alpha particles from radon are about 20 times as effective as X rays and gamma rays at causing breathing problems. Radium occurs naturally in earth rock’s and is made primarily of alpha particles. 

During the process of nuclear decay, the liberated energy is shared between the daughter nucleus and the alpha particle. Alpha particles dissipate their energy during collisions by two mechanisms: electron and ionization excitation. The alpha particle with high charge is relative to other forms of nuclear radiation and gives greater ionization power.

Uses of Alpha Particles

• They are used as smoke detectors.

• They are commonly used in space probes

• They are also used in radiotherapy to treat cancer.

Beta Particles

Beta particles are electrons which are smaller than alpha particles. They can easily penetrate through human skin or cause tissue damage. Beta particles can be inhaled if they contaminate food and water supplies. Beta-decay is the production of beta particles. Beta particles denoted by Greek letters (β).

They normally occur in nuclei that have too many neutrons to achieve stability. They have a mass of half of one-thousandth of the mass of a proton. Their light mass means that they lose energy very quickly through interaction with matter. Beta particles are also found in the radioactive products of nuclear fission. They are also found in the radioactive chain of thorium, uranium, and actinium.

Uses of Beta Particles

• They are used in thickness detectors for the quality control of thin materials.

• Fluorine-18 is used as a tracer for PET.

• They also help in the treatment of eye and bone cancers.

• Tritium is used for emergency lighting.

Gamma Rays

It is a packet of electromagnetic energy emitted by the nucleus of some radioactive elements. Photons of gamma rays are the most energetic photons in the electromagnetic spectrum. They are basically emitted from an excited nucleus. 

Waves of gamma rays have the shortest wavelength. The high energy of gamma rays enables them to pass through many kinds of material including human tissues. Radiations of gamma rays are penetrating and interact with matter through ionization. 

They are also easily found in the radiation decay of thorium, uranium, etc. Gamma radiations are easily found in rocks, soil, and in our water and food.

Uses of Gamma Rays

• Cobalt-60 used in industrial radiography

• They are also used in pasteurization

• Caesium-137 used in measurement and control of the flow of liquid in industrial processes.

• They are also used in leveling gauges for packaging of food, and other products.

The rotational motion of the body is analogous to its translational motion. Also, the terms that are used in rotational motion such as the angular velocity and angular acceleration are analogous to the terms velocity and acceleration that are used in translational motion. Thus, we can say that the rotation of a body about a fixed axis is analogous to the linear motion of a body in translational motion. In this section, we will discuss the kinematics kinematic quantities in rotational motion like the angular displacement θ, angular velocity ω angular acceleration α respectively corresponding to kinematic quantities in translational motion like displacement x, velocity v and acceleration a.

Rotational Kinematics Equations

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Let us consider an object undergoing rotational motion about a fixed axis, as shown in the figure, and take a particle P on the rotating object for analyzing its motion. Now as the object rotates about the axis passing through O, the particle P gets displaced from one point to another, such that the angular displacement of the particle is θ.

If at time t = 0, the angular displacement of the particle P is 0 and at time t, its angular displacement is equal to θ, then the total will be θ in time interval t.

Similar to velocity, the rate of change of displacement of the angular velocity is the rate of change of angular displacement with time.

Mathematically, angular velocity,

w = dθ/dt

Further, Similar to acceleration that rate of change velocity the angular acceleration of the particle P is defined as the rate of change of angular velocity of the object wrt time.

Mathematically, angular acceleration,

α = dω/dt

Hence, we see that the kinematic quantities in the rotational motion of the object P are angular displacement(θ), the angular velocity(ω) and the angular acceleration(α) that corresponds to displacement(s), velocity(v) and acceleration(a) in linear or translational motion.

Kinematic Equations of Rotational Motion

We have already learned in the kinematics equations of linear or translational motion with uniform acceleration.

The three equation of motion was,

v = v0+ at

x = x0 + v0t + (1/2) at²

v² = v02+ 2ax

Where x0  is the initial displacement and v0 is the initial velocity of the particle.v and x are velocity and displacement respectively at any time t and is the constant acceleration throughout the linear motion. Here initial means t = 0. Now, this equation corresponds to the kinematics equation of the rotational motion as well because we saw above how the kinematics of rotational and translational motion was analogous to each other.

ω = ω0+ αt

θ = θ0 + ω0t + (1/2) αt²

ω² =  ω0² + 2α (θ – θ0)

Where  θ0  is the initial angular displacement of the rotating particle or body, ω0 is the initial angular velocity and α is the constant angular acceleration of the body while ω and θ is the angular velocity and displacement respectively at any time t after the start of motion.

We come across many days today as examples of the relation between the kinematics of rotating body and its translational motion, one of which is if a motorcycle wheel has a large angular acceleration for a fairly long time, it is spinning rapidly and rotates through many revolutions. Thus we can say that, if the angular acceleration of the wheel is large for a long period of time t, then the final angular velocity ω and angle of rotation θ are also very large. The rotational motion of the wheel is analogous to the motorcycle’s large transnational acceleration produces a large final velocity, and also the distance traveled will be large. Also, we can relate the angular displacement θ and translation displacement by equation

S = 2πrN

Where N is the number of a complete rotation of particle chosen at any point on the wheel 

N = θ/2π