Category: Physics Notes PPT

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In this particular article we shall be learning about the following concepts – 

• An introduction

• What is Inertia?

• Types of Inertia

• Examples of Inertia 

• What is Momentum with examples

• Difference Between Momentum and Inertia

• Frequently asked questions

What is Inertia?

Newton’s first law

This law states that a body remains at rest or in the state of motion unless an effort or force is applied to make any change in its position.

For example, when we push a lawn roller, it starts dragging on the ground.

It means the force is applied to make changes in its position otherwise, it is in the rest position and would have remained at rest for an infinite period.

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Another example, a bob attached to the string when brought to either end from its mean position, and then set free, starts oscillating about its mean position. 

As it is kept in the air medium so, there will be an invisible air resistance acting on the pendulum. This will eventually bring the bob to rest. So, this air acts as an external force.

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Types of Inertia

According to Newton’s first law of the law of inertia, a body cannot make any change in its position, unless it is acted upon by an external force.

The inertia of a body is of three types:

1. Inertia of rest

2. Inertia of motion

3. Inertia of direction

Inertia of Rest

The resistance offered by a body to change in its state of rest. This means the body remains at rest and cannot start moving on its own.

Inertia of motion

The resistance offered by the body to change its state of uniform motion. This means the body is in uniform motion and can neither be accelerated nor retarded on its own, eventually comes to rest.

Inertia of Direction

The resistance offered by a body to change in its direction of motion along the straight line.

This means the body continues to traverse a linear path until some external force changes its direction of motion.

Inertia Examples

1. Inertia of Rest

The real-life examples of inertia at rest are outlined hereunder:

2. Inertia of Motion

• An airplane travels some distance on the ground before it can take-off. This is because it has a fixed aircraft wing, which can produce lift only when there is a relative velocity between the airplane and the air. 

          So, moving a certain distance, the airplane gains velocity.

3. Inertia of Direction

• When a knife is sharpened by pressing against a grinding wheel, the sparks fly off along the tangent to the grinding wheel, on account of the inertia of direction.

What is Momentum?

The momentum of a body or an object is the quantity of motion contained in it.

The quantity of motion in a body can be created or destroyed by the application of force on it; however, its momentum remains conserved. Therefore, it is measured by the force required to stop the body in a given time.

The force required to stop a moving body depends upon the following:

a. Mass of the Body

When a ball and a big piece of stone are made to fall from the same height, and at the same time. 

We found that a much greater force is required to stop the stone as it possesses greater mass. That’s why the stone has greater momentum.

b. The Velocity of the Body.

A bullet thrown with hands can be stopped easier than the same fired from the bullet. This is because velocity is greater in the latter case, therefore, with a larger velocity of the body, greater will be its momentum.

Momentum Examples

1. A truck and a car traveling at the same speed suddenly encounter a big rock on their way. Here, the truck will slow down long before the car.

By the relation, p = mv, the truck has a larger mass, but lesser velocity, so it will stop long before the car stops because the car has a large momentum.

2. A bullet of a smaller mass has a large momentum because of its extremely large velocity.

 

The Difference Between Momentum and Inertia

Key learnings from the chapter – 

• Inertia is based on Newton’s first law of motion. 

• A body remains at rest until a force is applied to change its position

• In Inertia of direction, the body moves in the linear path until a force is applied to change its direction

• Momentum is the product of mass and velocity. The force of momentum is directly pro
  portional to the mass and velocity. Larger the mass, the more the momentum. Similarly, more the velocity means higher momentum

• Thus, momentum is the tendency of an object to remain in motion while the inertia of an object has the tendency to oppose the changes.

The terms ‘sensor’ and ‘transducer’ are often used to describe the same devices that are mentioned as “linear sensor” and “linear transducer”. They refer to the same component. However, in some cases, the terms sensor and transducer have different meanings and there are some differences which are between the two terms.

Here, we are going to discover a few more things about the topic mentioned and discover more and more about transducers and sensors.

Sensor and Transducer Difference

The transducers that we are discussing can be measured in similar qualities to a sensor but gradually convert the signal from one physical form to another, meaning their output and input signals are not the same as each other. The transducers are sometimes referred to as energy converters.

There are different types of transducers, these include the input transducers and the output transducers. An input transducer generally takes a form of energy and converts it into electrical signals. An output transducer takes electricity and converts it into another form of energy – for example, a light bulb takes electricity and converts it to light or a motor converts electricity to motion. These transducers sense a change and then the transform takes energy from one form to another. Usually, that is from non-electrical to electrical or vice versa.

The Pressure transducer and cable extension transducer along with the linear transducer and control of a microphone engine controls and HVAC monitoring, steering systems that are on the vehicles and their ramp or bridge lifting or positioning.

Sensors are defined as devices that are used to measure a physical quality for example its sound, light, temperature, etc., and give the output in an easy-to-read format for the user.

Sensors sense the changes and give readings in the same format that the signals are received. An additional device will be needed to convert the energy which is supposed to be required. The switches pressure and the thermistors, mercury thermometers are motion sensors. The toilet infrared flushes, pressure level in oxygen tanks monitoring patients are sensors.

Transducer and Sensor Applications

The sensor is said to be a device that measures the physical quantity, that is light, heat, sound, etc. into easy signals which are readable voltage, current, etc. It is said to give accurate readings that are after calibration.

For example, the mercury that is used in the thermometer converts the temperature which is measured into an expansion and contraction of the liquid which is easily measured with the help of a calibrated tube of glass.

The thermocouple is also said to convert the temperature to a voltage which is output which is measured by the thermometer.

The sensors that we are studying already have many applications in electronics equipment. A few of the applications are explained below.

1. The motion sensors are used in the security of the home system and the automation door system.

2. Photo sensing the infrared or ultraviolet light.

3. The accelerometer of the sensor is used in the mobile for detecting the screen rotations.

Sensor Transducer Difference in Working

The transducer is a device that changes the attribute – the physical or the non-electrical signal to an electrical signal which is easily measurable. The process of conversion of the energy conversion in the transducer is called transduction. The transduction is said to be completed in two steps. First by sensing the signal and then strengthening it for further processing.

The transducer and the sensor both are devices that are physically used for measuring the quantities which are physical like temperature, heat, displacement, etc. which are very difficult to measure. The transducer is said to have three major components: they are the input device signal that conditions, a device that is processing, and an output device.

The devices which are input devices receive the measured quantity and transfer the proportional analog signals to the conditioning device. The conditioning devices which are modified, filtered, or at times attenuates the signal which is easily acceptable by the devices which are said to be the output devices.

Electromagnets are soft iron cores that are made into magnets on passing an electric current through the coil surrounding them. 

A permanent magnet is something that is an innate ability of a magnet that continues to show magnetism even if it is removed from the magnetic field. 

So, here if we differentiate between an electromagnet and a permanent magnet, it seems that permanent magnets are better than electromagnets; however, each of these has its own advantages. 

This article discusses the difference between an electromagnet and a permanent magnet in points.

Electromagnetism Meaning 

The word ‘Electro’ in electromagnetism talks about the magnetism that is caused by the effect of electricity, and soon it loses its magnetism when it is brought away from the area of the magnetic field.

Permanent Magnetism Meaning

The word permanent talks about something that remains firm or permanent. Here, permanent magnetism means a magnet that retains its magnetism after the removal of the magnetizing force or after taking a magnet from the vicinity of the magnetic field. 

The below diagram represents the difference between the electromagnet and permanent magnet:

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Differentiate Between Permanent Magnet and Electromagnet

Distinguish Between the Electromagnet and Permanent Magnet:

Now, let’s discuss more to differentiate between the electromagnet and permanent magnet:

The table below lists the difference between the electromagnet and permanent magnet

Difference between Permanent and Electromagnet

Uses and Advantages of using Permanent Magnet

The permanent magnets are particularly efficient at attracting other magnetic objects and a lot of modern appliances need to convert the mechanical motion into a kind of force or energy to work. One of such appliances is inductions and generators. They convert the motion into energy with the help of permanent magnets. They are also used in televisions, speakers, or headphones as they need to create a magnetic field around them to work. 

Permanent magnets are also not so expensive and that is why the usages of permanent magnets in the industrial sectors prove to be quite a good idea. They are portable and consume less space. The best part of permanent magnets is that they do not need a separate wiring system in order to create the magnetic field and that is why their manufacturing cost is also quite low compared to the electromagnets.

The appliances that incorporate permanent magnets into their system can be used in various ways and multiple times and that is why they are quite cost-effective. Since permanent magnets do not need any external power supply or force to create the magnetic field, variation in the power of the magnetic field in different areas cannot be seen. Using permanent magnets can provide you with a uniform magnetic field.

In this article, you will learn the behavior of the forces performing on a dipole in a uniform magnetic field and will correlate it with the situation when a dipole is retained in an electrostatic field. For example, we experience that if we keep the iron fillings near a bar magnet upon a piece of paper and pound the sheet, the fillings assemble themselves to create a particular design. Here, the arrangement of iron filings signifies the magnetic field lines produced by the magnet. These lines generated due to the magnetic field provide us a fairly accurate clue of the magnetic field. On the other hand, most often, we are prescribed to govern the amount of magnetic field B precisely. We achieve this by employing a small compass needle of identified magnetic moment (m) and moment of inertia and let it oscillate in that particular magnetic field.

The region around a magnet within which another magnet can influence is called the Magnetic Field . A series of lines around a magnet is represented as a magnetic field. The magnetic field is one of the most important topics of physics.

Apart from the book, we also use a magnetic field in our daily life. Let us get familiar with the term and enjoy the study of . Students are going to have fun when they know about the uses. Here are some uses like

Computer hard disk

• Television

• Radio

• Telephone

• Microwaves oven.

A pair of two equal and opposite forces having a different line of action gives rise to a turning effect known as torque along the axis, which is perpendicular to the plane of the force.

Students can describe the magnetic influence on moving electric charges; electric currents and magnetic materials are magnetic fields. It is a vector field. A moving charge present in a magnetic field experiences a force perpendicular to its velocity and the magnetic field.

A magnetic field permanent magnets pull on ferromagnetic materials such as iron and attract or repel other magnets. Also, a magnetic field that varies with location will exert a force on a range in respect to non-magnetic materials by affecting the motion of their outer atomic electrons. Those Magnetic fields surrounding magnetized materials are created by electric currents such as those used in electromagnets and electric fields may vary in time. 

The strength and direction of a magnetic field may sometimes vary with location; it is described by a function assigning a vector mathematically to each point of space, called a vector field.

Torque on a Magnetic Dipole in a Uniform Magnetic Field

Usually, a Magnetic dipole is a small magnet of atomic to subatomic sizes, similar to a flow of electric charge around a loop. Electrons rotating on their axes, electrons passing around atomic nuclei, and spinning positively charged atomic nuclei all are magnetic dipoles.

The addition of these effects may cancel so that a specified type of atom may not be a magnetic dipole. If they do not fully cancel, the atom is an everlasting magnetic dipole. Such dipoles are iron atoms. Millions of iron atoms locked with the same arrangement spontaneously creating a ferromagnetic domain also create a magnetic dipole.

Magnetic compass needles, and magnetic bars are examples of macroscopic magnetic dipoles.

Let’s take a magnet bar (N-S) having the length 2l and the pole strength m located in a uniform magnetic field of induction denoted as B by creating an angle θ with the field direction, as shown in the figure below. Because of this magnetic field denoted by B, the first force (m ∗ B) executes on the North Pole along the magnetic field direction, and another force (m ∗ B) executes on the South Pole along the opposite direction to the magnetic field. These two new forces are identical and inverse,

Therefore it establishes a couple.

Torque on a Magnetic Dipole in a Uniform Field

When a magnetic rod, (which can be taken as a magnetic dipole), is kept in a uniform magnetic field, the North Pole senses a force equal to the multiplication of the magnetic field intensity and the pole strength in the magnetic field direction.

Nonetheless, the South Pole senses a force, equal in magnitude but opposite in direction. Hence a torque exerts on the magnetic dipole because of which the magnet starts to rotate.

The torque is denoted as τ because the couple is:

τ = Force ∗ Perpendicular distance 

= F ∗ NA——(1)

We know, F = m ∗ B

So,  = mB ∗ 2l sin θ

 = MB sin θ——(2)

It can be written in the vector form

as  τ  = [M^{rightarrow}* B^{rightarrow}] 

We also know that the direction of τ is perpendicular to the plane and;

If θ = [90^{0}] and B = 1

Then we can obtain from equation (2), τ = M 

Thus, the torque, which is essential to keep the magnet at [90^{0}] with a magnetic field, is equal to the magnetic moment induction.

Electrostatic Analog

Let’s compare the equation of electric dipole in an electric field. We conclude that the magnetic field due to a bar magnet at a considerable distance is analogous to an electric dipole in an electric field. Likewise, the relation can be status as given below,

E→B,p→m,[frac{1}{4pivarepsilon_{0}}rightarrow mu_{0}4pi Erightarrow B], ,p→m,[frac{1}{4pivarepsilon_{0}}rightarrow mu_{0}4pi]

If the value of r, that is, the distance of the point from the given magnet, is tremendous as compared to the size of the magnet given by I, or r >> l, then students can write the equatorial field generated by a bar magnet as,

B_E=−[frac{mu_{0}m}{4pi r}]

3B_E=−[frac{mu_{0}m}{4pi r^{3}}]

Comparably, the axial field of the bar magnet in the same condition can be given as,

B_A=−[frac{mu_{0}2m}{4pi r}]

3B_A=−[frac{mu_{0}2m}{4pi r^{3}}]

Stay updated with to learn more about dipoles in a uniform magnetic field, the electrostatic analog, and other related topics.

Drag Force Animation

Friction is the force that prevents rigid surfaces, fluid layers, and material elements from slipping against each other from moving in the same direction.

 

Several Types of Friction

• The relative lateral motion of two solid surfaces in contact is resisted by dry friction.

• The friction between layers of a viscous fluid that are moving relative to each other is referred to as fluid friction.

• Lubricated friction occurs when two rigid surfaces are separated by a lubricant fluid.

• Skin friction is a part of drag, which is the force that prevents a fluid from moving over a body’s surface.

• Internal friction is the force that opposes motion between the components that make up a solid material as it deforms.

 

What is Fluid Friction?

Fluid friction happens as two fluid layers move in opposite directions. Viscosity is the term for the internal resistance to flow. The viscosity of a fluid is often referred to as its “thickness.”

All real fluids are viscous because they resist shearing in any way. The definition of an inviscid fluid, or an ideal fluid that gives no resistance to shearing and is therefore not viscous, can be useful.

 

Examples of Fluid Friction

• If there is a wet surface between two thin glass plates, the plates will get trapped and the bottom plate will not break when only the top plate is held.

• The extent of a splash when an object is dropped in a fluid is determined by the fluid friction of that fluid.

• On the surface of moving water, lighter dust particles travel quickly. This is because the top layer of water has a high-velocity gradient due to lower dynamic fluid friction.

 

Drag Force Formula

The force that is exerted on a rigid body moving with respect to a fluid due to the fluid’s movement is known as drag force. For instance, drag on a moving ship in the water or drag on a moving plane in the air. As a result, a drag force is the resistance force created by a body moving through a fluid such as water or air. This drag force is directed in the opposite direction as the oncoming flow velocity. As a result, the relative velocity between the body and the fluid is this.

 

Concept of Drag Force

A fluid’s drag force is its resistance force. This force acts in the opposite direction of the motion of an object that is submerged in a fluid. As a result, drag force is described as the force that opposes a body’s motion through a fluid.

Aerodynamic drag occurs when such motion of the body occurs in the fluid-like air. It’s also a hydrodynamic drag if the fluid is water. Its natural tendency is to behave in the opposite direction of the velocity flow.

The maximum speed that a falling body can achieve is often limited by air resistance. The drag force, which is the force that objects experience when moving through a fluid, is exemplified here by air resistance.

Drag force, like kinetic friction, is reactive in that it only occurs while an object is moving and points in the opposite direction of the object’s motion through the fluid.

This force is divided into two categories: shape drag and skin drag. The resistance of fluids to being moved out of the way by an object moving through the fluid causes form drag.

As a result, shape drag is close to the usual force given by solids’ resistance to deformation. Skin drag is basically a mechanical frictional force induced by the fluid slipping over the moving object’s surface.

Fluid density, Square of velocity, Drag coefficient, and Cross-section area all have an effect on its value.

 

What is Drag in Science?

Drag is the force that a fluid stream exerts on some object in its direction or that an object passing through a fluid feels. Designers of moving cars, ships, suspension bridges, cooling towers, and other structures must consider its size and how it can be minimized. Traditionally, drag forces are represented by a drag coefficient, which is determined regardless of the shape of the body. Dimensional analysis shows that the drag coefficient is proportional to the Reynolds number; the exact relationship must be determined experimentally, but it can be used to estimate the drag forces encountered by other bodies in other fluids at different speeds. When engineers use the effects of a model structure to predict the behavior of other structures, they use the concept of dynamic similarity.

What is a Magnet?

Magnet is a device/object that produces an external magnetic field. It applies force over other magnets, charges, electrical current, and magnetic material. There are several types of magnets. Permanent magnets are the ones which do not lose their magnetism. The majority of the magnets you see are man-made around you. Since they were not initially magnetic, they have lost their magnetic properties over time. For example, dropping them weakens their magnetism. Most of the man-made magnets were originally non-magnetic, and so they lose their magnetic character with time. 

What is a Magnetic Field?

The magnetic field is an invisible field around a magnet or magnetic object, in which magnetic force is exerted. The invisible area around a magnetic object can pull up another magnetic object or push away another magnetic object. Moving electric charge generates magnetic fields. A magnetic field can be produced when electrons, which have a negative charge, move about in some certain direction. Magnetic fields can be represented by the continuous line of forces that emerge from the north pole of the magnet and enter into the south pole of the magnet and vice-versa inside the magnet. The density of the lines shows the magnitude of the magnetic field at any point.  

Mathematically, the magnetic field can be defined in terms of the amount of force exerted on a moving charge in a magnetic field. This force can be measured with the help of Lorentz Force law, 

F = qvB

Where,

F-Force exerted on the moving charge

q-the amount of charge

v-velocity of the moving charge

B-Magnitude of the magnetic field

Here, this relationship is a vector product, and the force is perpendicular to all other values.

Effect of Magnetic Field on a Current-Carrying Wire

Electric energy is transmitted by the current, which is basically the flow of the electrons, which are the sub-particles of the atom and are negatively charged. This movement of electrons from one location to another power our lights, computers, appliances, and many other things. Another fascinating fact about electric current is that it produces its own magnetic field.  Magnetism and electricity have a close relation in that all closed-loop currents generate their own magnetic fields, and magnetic fields acting on closed-loop circuits may produce current. The magnetic effect of electric current was discovered by Oersted.

Experiment: How Magnetic Field Affects Current-Carrying Wire?

Materials 

Procedure

• Remove 1 inch of insulation of the wire from each side.

• Place the horseshoe magnet onto a flat surface on its side.

• Using a tiny piece of electrical tape to tape the metal portion of one end of the wire through the battery’s negative terminal.

• Move the horseshoe magnet wire between the legs.

• Holding the insulated portion of the wire, connect the wire’s open end to the positive battery terminal. What direction is the movement of the electric current? Why do you have to maintain wire insulation instead of metal? List your findings.

• Flip over the magnet and repeat the procedure. How, if anything, will change? Document your thoughts.

Results

The wire would bend away from the magnet’s poles.

Why this Happens

As we know, electric currents always produce their own magnetic fields. The behavior and the direction of the current can always be described by the right-hand rule. Simply point your thumb towards the direction of current flow, and curl your fingers around the wire, the direction of the curl fingers will give the direction of the magnetic field as shown below in the figure. 

That means you also change the direction of the magnetic field when you change the direction of the current. Magnets have two poles, South and North, like the horseshoe magnet used in this exercise. The term ‘attracting opposites’ refers to magnets; thus, interactions between north and south hold together, and interactions between north and north and south and south repel or move away from each other. 

Fun Facts

• The north pole and south pole of a magnet cannot be separated. Cutting one magnet in half makes two magnets, with two poles each.

• Earth’s magnetic field is around 1,000 times weaker than the typical bar magnet.

• Cranes use huge electromagnets to pick up scrap metal in junkyards.

• Electromagnets use electricity to generate their magnetic power. When the electricity is turned on and off, the magnetic power can be turned on and off.

• If you attach a bar magnet to a piece of wood and place it in a water bath, it will gradually turn into the water until the North Pole of the magnet points towards the North Pole of our planet. Temporary magnets are used to do the same.