Category: Physics Notes PPT

To answer the question, what is a gear? We can say that a gear is a kind of machine element which has teeth cut around a cylindrical or cone-shaped surface with equal spacing? They are used to transmit rotations and forces from the driving shaft to the driven shaft when a pair of these elements have meshed. There are different types of gear. They have a different basis of classification. The history of gears is old and is mentioned by Archimedes to be in use in ancient Greece in B.C.

 

Classification of Gears and their Application

All types of gears are given in the classification chart below.

 

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Gears can be classified as parallel shaft gears, intersecting shaft gears and non-intersecting non-parallel shaft gears depending on the position of their axes. 

Some important gears are given in detail below.

1. Internal gear

2. Screw gear

3. Worm gear

4. Bevel gear

5. Spiral bevel gear

6. Spur gear

7. Mitre gear

8. Gear rack

9. Helical gear

Each type of gear is discussed in brief below:

1. Internal Gear

These gears have teeth cut on the inside part of cones and cylinders and are used to pair with external gears. These are used in shaft couplings which are of gear types and planetary gear drives. Due to trimming problems and interference such as trochoid and involute, there lies one disadvantage with this gear, which is an unequal number of internal and external gears.

2. Screw Gear

Screw gears or sometimes called crossed helical gears are helical gears used in motion transmission between non-intersecting shafts. In parallel shafts, the helical gears used have the same helix angle but in opposite directions. It consists of the same hand helical gears at an angle of 45 degrees on the non-intersecting and non-parallel shafts. It is used for small power transmission.

3. Worm Gear

It consists of two elements, a screw-shaped cut on the shaft called a worm and the other one is a mating gear called a worm wheel. These two together on a non-intersecting shaft form worm gear. material is used for worm and a soft one for worm wheels as it is necessary to reduce friction due to sliding contact of surfaces. They can have a cylindrical shape and also an hourglass type which increases the contact ratio but reduces the production.

4. Mitre Gear 

These are basic bevel gears with a speed ratio of 1. The direction of power transmission is changed by them without changing speed. They can be both straight and spiral. With spiral mitre gear thrust bearing is also used as it produces thrust force in the axial direction. Mitre gears with shaft angles other than 90° are called angular mitre gears.

5. Bevel Gear

These have a cone shape at their pitch surface and teeth are cut along the cone. They transmit force between two shafts that intersect at a point. Various kinds of bevel gears are helical bevel gears, spiral bevel gears, straight bevel gears, mitre gears, angular bevel gears, zero gears, hypoid gears and crowns bevel gears.

6. Spiral Bevel Gear

Bevel gears with curved tooth lines are called spiral bevel gears. They are superior to straight bevel gears in efficiency, strength, vibration and noise due to higher contact ratio but are difficult to produce. Since teeth are curved, it produces thrust force in the axial direction. These gears with zero twisting angles are called zerol bevel gears.

7. Spur Gear

Spur gears are included in the parallel shaft gear group. They are cylindrical gears having tooth lines straight and parallel to the shaft. Cylindrical gears are gears with cylindrical pitch surfaces. In meshing pairs, the larger one is called gear and the smaller one is pinion. They achieve high accuracy and are relatively easy to produce.

8. Gear Rack

A gear rack consists of same sized and shaped teeth cut at equal distances along a flat surface or a straight rod. It is a cylindrical gear having a radius of pitch infinity. It converts rotational motion into linear motion by meshing with a cylindrical gear pinion. Straight tooth racks and helical tooth racks are its broader classification.

9. Helical Gear 

These gears can transmit high loads. They are very quiet and are cylindrical gear with winding tooth lines. Its two subdivisions are left-hand twist and right-hand twist.

 

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Different Types and Applications of Gears

Since gears are an essential part of many devices, tools and vehicles they have a wide range of applications. Everywhere different types of gears are used as per the requirement. Thus applications of gears are given below as per the types of gears.

 

Fun Facts about Types of Gears and Their Applications:

Studying gear can become tiresome after a point in time. To get you out of this
boredom has brought some facts about gear:

• The first gear was made of wood. They were applied in watermills and windmills.

• Metal gears were used for the first time in the clocks.

• Gears used in cars are known as helical.

• Some gears are not circular in shape. Some of them are conical and square.

• The largest gear in the world weighs 73.5 tons and is 13.2 m in diameter.

• Roller coasters cannot work without gears

• An insect named Issus has gears in its hind legs which allows the legs to function together in synchronized motion when the insect jumps. This is an example of natural gear.

Conclusion:

The topic of gears forms an essential part of mechanics and a lot of questions are asked from this topic in various examinations including engineering exams in higher standards. The above write-up covers the topic of Types of Gears Their Applications in great detail. It starts with the definition of gear and goes on to cover topics like its types, classification, applications, etc. After reading this write-up you will be in a position to understand the basics of the chapter and also well prepared to grasp advanced concepts related to the topic.

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Sound travels only through a medium and you can hear it only when the frequency of sound is within the audible range. For human beings, it is between 20Hz to 20KHz and it differs for every other living creature. However, students should note that sounds below and beyond this range are not audible to the human ear.

Although sounds of such high and low frequency exist, the human ear does not perceive it. You might have heard about bats being able to identify such sounds that the human ear is unable to trace. This is the most real-life application of ultrasound, and that is how they navigate through the dark. This stands true even though most of us have been learning it since childhood. 

Sound waves whose frequencies are above the upper audible limit of any human hearing are called ultrasound. It’s limit varies from person to person but it is approximately 20,000 Hertz. The physical properties of ultrasound are almost similar to the traditional audible sound. This type of concept which is scientific is being employed in a lot of fields like medicine, imaging, mixing, communication, navigation, testing, cleaning etc. Even if we talk about nature, bats and porpoises use this same technique for the situation of prey and obstacles.

What is the Ultrasonic Sound?

As already mentioned, sound can be beyond and below the human audible range. So, any sound that is higher than this range is called the ultrasonic sound. The application of ultrasonic sound is not just numerous, it is also highly beneficial.

Students are required to understand each application of ultrasonic waves in different fields for a clear understanding of this concept. Some of the common areas are medical, navigation, cleaning, etc. All these ultrasound uses are unique and have their respective areas of use.

What are the Applications of Ultrasonic Sound?

Ultrasonic sound has various applications in multiple fields due to its precision in results. It has been in use for a long time, and with the passage of time, it has only gained momentum. Scientists have found newer applications in the field of medical sciences, notably being that of treating patients and conducting minor surgeries. 

What is Ultrasound Used for?

Commonly practiced application of ultrasonic waves is in conducting ultrasonography. It is an imaging technique which is used by doctors to check on a developing baby.

Probably one of the most common uses of ultrasonic sound is echolocation. The flying mammals or bats use this locating technique to navigate to their prey in the dark.

Echocardiography or what is precisely known as ECG is another popular medical application of ultrasound. Again an imaging technique, here the sound waves travel inside the body to present an image of the condition of a patient’s heart.

Cleaning of spiral tubes and various electronic components are other applications of ultrasonic waves in physics. The materials to be cleaned are put in a liquid where such ultrasound is passed, and cleaning is carried out.

Another ultrasonic sound and its application is in the detection of cracks. Usually, cracks or fissures in high buildings and significant metal components are detected through waves. 

Among other significant areas for application of ultrasound, a major one is that of conducting lithotripsy. It is the process of breaking stones in the kidney by passing waves of high frequency.

Submarines use this technique of passing high-frequency waves under water for navigational purposes. These sound waves can easily travel in water and are used for communication and detection of other submarines as well. 

Therefore, when you look for what are the uses of ultrasound, read about other applications too. It will help you in building a stronghold on the topics. Related concepts must also be read since this topic has innumerable applications.

To know more about ultrasound and its applications, you can look into our online study programs. Besides, you can also download our app available for both iOS and Android users. The app can be especially helpful in understanding the application of ultrasound and related topics from the ease of your home.

The standard unit of electricity is defined in a systematic way. First, the ampere is defined. After, the ampere comes from the charge and coulomb of an electron.

 

The SI units to measure the electric expressions of voltage, resistance and current are Volt (v), Ohm (Ω) and Ampere (A), respectively.

 

The electrical units for measurement of electric expressions are based on the International System (SI) of units. Other units are derived from this si unit of electricity.

 

The units are used in electric circuits, electronics and electric appliances to measure and describe their capacity from small to large.

 

Standard Electrical Units of Measure

 

Standard Units (Multiples And Submultiples)

There is a huge range of electric values between a minimum value and a maximum value of a standard electric unit. For example, the resistance of a conductor can be as low as 0.001 ohms and as high as 100000 ohms. We can avoid writing multiple zeros while describing the values of the electric unit, if we use sub-multiples and multiple values of the standard unit. Below mentioned is a table with their names and abbreviation.

 

 

Below mentioned is a set of points that describes the use of units or multiple units of resistance, current and voltage.

● 1kV = 1 kilo-volt = 1,000 Volts.

● 1kΩ = 1 kilo-ohms = 1 thousand Ohms.

● 1mA = 1 milli-amp = one-thousandths (1/1000) of an Ampere.

● 1kW = 1 kilo-watt = 1,000 Watts.

● 100uF = 100 microfarads = 100 millionths (100/1,000,000) of a Farad.

● 1MHz = 1 mega-hertz = one million Hertz.

 

While converting one prefix to another, we have to multiply or divide the difference between the two values.

 

What Are The Basic Units Of Electricity?

Voltage/Volts (V) – The amount of work required to move an electric charge from one point to another is called voltage.

 

Current (I)/Amps (A) – Current is defined as the amount of charge (or electrons) passing through a circuit per unit of time.

 

Resistance (R) /Ohms (O) – Resistance is the opposition offered to the flow of current in a circuit.

 

Power (P)/Watts (W) – Power is defined as the product of the work required and the number of electrons passing through the circuit per unit time.

 

Other Electricity Units

Just like the standard units, other units are used to denote the values and quantities. They are:

 

Wh – The Watt-Hour is defined as the amount of electric energy consumed by an electric circuit over a given time duration. For example, a normal electric bulb consumes 100 watts of power per hour.

 

dB – A Decibel is a one-tenth unit of Bel (symbol B). It is used to represent a gain in voltage, power or current.

 

θ – Phase Angle. It is the difference (in degrees) between the voltage waveform and the current waveform, which have the same time period. It is a time difference that depends upon the circuit element. Its value can be “leading” or “lagging”. It is also measured in radians.

 

ω – Angular Frequency is used in AC circuits to represent phase relation between two waveforms.

 

τ – Time Constant, The Time Constant is a characteristic of an impedance circuit. It is the time taken by the output to reach 63.7% of its minimum or maximum value when subjected to step response input. It is a measure of time reaction.

 

SI Unit of charge

The SI unit of electric charge is the coulomb. A coulomb is defined as an ampere second.

 

The Units of Electric Charge are Listed in The Table Mentioned Below

These are the units of electric charge.

 

Do You Know?

There is nothing like “1 unit electricity”.

 

Throughout the world, there is one type or another type of measurement which has been taken as a base amount of electric power. 1KWh is a mainly used unit of power. It is the amount of electric power consumed in 1 hour by an electric appliance of 1000 W (1KW).

 

Electricity is Measured in Units of Electricity.

If you’ve ever looked at an electricity bill, you’ll notice that the unit of electricity is usually expressed in kilowatt-hours (kWh). The unit, in this case, reflects the actual measure of electricity or the amount of energy consumed at a location. So, if you’ve ever wondered what the unit of electricity is, the answer is below.

Electricity is Measured in Units of SI.

When it comes to the SI unit of electricity, the unit of power is Watt. The name was preserved in honor of James Watt, the inventor of the steam engine. Watt is usually equal to one ampere under one volt of pressure, however, electricity, which is a bigger quantity, is measured in kilowatt-hours (kWh).

The Volt [V], Ampere [A], and Ohm [] are the standard units of electrical measurement for voltage, current, and resistance, respectively.

Other commonly used electrical units are derived from SI base units. These electrical units of measurement are based on the International (metric) System, generally known as the SI System.

When the amounts being measured are very big or very small, it is often essential to employ multiples or sub-multiples (fractions) of these basic electrical measuring units in electrical or electronic circuits and systems.

Electrical Units of Measurement

What Are The Four Basic Electricity Units?

The four fundamental units of electricity are:

• Voltage is the amount of effort necessary to transfer one electric charge from one location to another. The volt is the measurement unit.

• Current is the amount of charge that passes through a circuit in a certain amount of time. The unit is ampere.

• The opposition provided by the current flow in the circuit is known as resistance. The units are ohms.

• The product of work done and the number of electrons travelling through the circuit in a certain amount of time is called power. The watt is the measurement unit.

Volts, amps, ohms, and watts are the four basic units of electricity.

Stay tuned to for further information on other concepts, such as the volt.

Units of Electricity (Others)

There are other conventional units of measurement for electrical qualities other than watt and kilowatt, such as voltage, resistance, power, capacitance, inductance, and others. Some common electricity units are listed below.

The force which is applied to any object to make it rotate is the moment of force or torque. When the motion of an object over distances is greater than its own size, these bodies are considered as point objects, we use kinematics to describe the motion of these point-sized objects in one, two, and three-dimension,  and some work is required to make changes in the configuration and motion of these objects.

Torque is the moment of force that enables a body to rotate on its own axis and gain angular acceleration. The SI unit of Torque is N.m. It is a vector quantity and can be both static and dynamic. In the following sections, we will learn about the units of torque in detail. Torque is also known as turning effect, rotational effect, a moment of force, or moment.

If the magnitude of a body is lower than the movement of an object over a specific distance then it is known as a point object. The motion of the point objects is described in one, two, and three dimensions with the help of kinematics. The point objects are made up of usually very large particles. The rotational behavior of these boundless particles is described by Newton’s Law of Motion.

Contents of the Article

This article explains to you the meaning of torque, its importance, and its units. If you incur any doubts while reading this, then you can simply refer to the frequently asked questions at the end of this article.

On this Page, We will Learn

• Unit of torque

• S.I. unit of torque

• CGS unit of torque

• Other units of torque

• S.I. base unit of torque

You come across these Objects Daily but are They Point-Sized in Actual?

Well, the objects we see in real-life aren’t point-sized in an absolute sense. These objects have a bounded size, made up of very large particles.

Here, we would extend the application of Newton’s laws of motion to describe the rotational motion of these finite-sized objects. Since there are many particles inside the object interacting with each other, these interacting particles together form a system. Thus, any object of finite size forms a system.

A large body that is made of many particles has a center of mass which states that the mass of the system of the body is supposed to be concentrated at the center. If an external force is applied then the center of mass remains the same or unaffected.

What is an External Force?

We studied in the chapter laws of motion that when a force (H) is applied to any object of mass(k), the object starts accelerating. The statement can be represented by the equation: H= k x b

Where b is the acceleration, H is the force, k is the mass

Similarly, When you switch on a fan, the center of the fan remains unmoved, while the fan rotates with angular acceleration. Now this center that remains unmoved is the center of mass of the fan that remains at rest. You might be wondering that the force we studied in the above relation H=k x b was for applying a force to the bodies in linear motion, then which kind of force is responsible for producing angular acceleration?

Angular Acceleration

Torque is a measure of the ability of a force to bring the body in rotation. Just as a net force causes acceleration, a net torque causes angular acceleration, where angular acceleration is the rate of change of angular velocity (the velocity at which the body sweeps an angle Ө per unit time). Given by :

Angular acceleration(s) = change in angular velocity (df) w.r.t time (g) = df/dg

The Formula of Torque

Torque = force x distance

Torque = rF sin θ

Where, r= radius, F = force,  θ= angle between lever arm.

Torque or Moment of Force

The object starts rotating about the fixed point or the axis of rotation when an external force is applied. The force applied is called the torque.

In figure.2, we can see that as soon as the external force or torque or moment of force is applied. The twisting of this object is about the axis of rotation which is measured by the product of the magnitude of the force H and the perpendicular distance (k) of the action of a force from the axis of rotation. The torque is represented by the Greek letter N. The statement is represented by the equation given below:

[vec{N}=vec{H}times vec{k}=kN sintheta hat{n}]

Where Ө is the angle between [vec{k}]  and  [vec{H}].  n is the unit vector along  [vec{N}].

Here, the direction of  [vec{N}]  is perpendicular to the plane containing [vec{k}]  and  [vec{H}].

So you can consider torque as the angular equivalent of force. Torque brings forces into the kinematics of the rotational world.

Why is Torque so Important?

Torque is a fundamental concept of physics (as an attribute of force or the moment of force applied in the concepts of rotational motion of rigid bodies) that helps us apprehend how things happen around us. With the help of torque, it can be dictated what the direction and magnitude of a rotational force applied on an object are, allowing you to evaluate the results it may generate. Basically, torque can help you determine whether the force applied will result in a counterclockwise or clockwise motion.

Torque also helps you to predict the angular acceleration from which the object is being rotated. Since torque can be large or small, it is measured in different units as described below in the table

Importance of Torque

• Torque explains the concept of the rotational motion of rigid bodies. 

• The direction and intention of the force applied to a body can be detected by the concept of torque. 

• It also determines the clockwise and anti-clockwise motions on a body. 

• Torque also determines the angular acceleration when a body rotates.

Units of Torque in MKS and Dimension

Different Units of Torque

• The SI unit of torque is a newton-meter. 

• The SI base unit of torque is kgm²sec^-2.

• The non-SI unit of torque is meter-kilogram-force

• In the CGS system, the unit of Torque is dyne-centimeter (dyne-cm)

Other units of Torque

Real-life Applications of Torque

Old Telephone

We used to rotate the numbers on the dial in a clockwise or counterclockwise direction. Torque is making that rotational push that is exerted by our fingers on the dial.

Ferris Wheel

The wheel of the Ferris wheel is rotating about its axis, the torque is pushing this wheel to make a rotation.

Lock-Key

When you twist the key inside the lock, the lock opens. The torque is creating the twisting motion that is put on the key.

Summary

The torque is required only for creating angular acceleration in the body, but for uniform rotation, no torque is needed.

Torque is just a force that is applied to the axis of rotation with the center of mass of an object, a force applied a distance ‘k’ away from the center of mass, which causes an object to rotate. Torque is responsible for producing angular acceleration in the body. A bigger force means a bigger torque, and a larger distance from the fixed point also means a bigger torque.

A human is a natural optical lens that helps us see real-life objects with exact color distinctions. 

However, a few people lose the ability to see far/near objects, for them, a concave/convex lens (resp.) works as a helping source to fulfill their clear vision dreams.

A concave lens is a diverging lens that helps people view objects at large distances if they are dealing with Myopia; however, for people dealing with hypermetropia, a converging lens, convex lens is used, which we will discuss in this article.

We will also discuss the application of concave lenses with the uses of a concave and convex lens.

Concave Lens

A concave lens is one that is thicker at the edges and thinner in the centre. This type of lens bends light rays outwards. A concave lens is also known as a diverging lens as it diverges the light rays. It is made up of a number of prisms, with the base of each prism pointing away from the lens’s centre. The lens’s central section is a simple parallel-sided glass.

Light rays can pass through the parallel-sided glass slab without deviating.

The upper portion of the lens deviates light rays upwards, while the lower portion deviates light rays downwards. These lenses are used in those types of glasses that are known to correct the defects of vision i.e., myopia and hypermetropia. Materials used to make these lenses can either be glass or plastic, which are then polished and eventually moulded into different shapes. In contrast to a prism, which refracts light without focusing, a lens can focus light to form an image. 

Types of Concave Lens

The following are the different types of concave lenses:

1. Double concave

2. Plano concave

3. Convexo-concave

The Formula of Concave Lens

To know which type of image is created by a concave lens, the lens formula of that concave lens is used. It is also used to identify the position of the image. The formula for the concave lens is as follows:

1/f=1/v +1/u

Where,

‘f’ = the focal length 

‘v’ = distance of the image. 

‘u’ = distance of the object. 

Uses of Concave Lens

1. In a Telescope

Concave lenses are magnifiers found in telescopes and binoculars. The object is magnified by the concave lenses. Concave lenses are used before or in the eyepiece of telescopes and binoculars to help people focus more clearly.

2. Applied to Glasses

Concave lenses are used to correct myopia, also known as nearsightedness. Concave lenses in spectacles are used to compensate for the shortage by spreading light rays out before they reach the eyeball. This improves the person’s ability to see items in the distance.

3. In use in Peepholes

Peepholes are security devices that provide a 360-degree view of objects or areas outside of walls or doors. They are also known as door viewers. A concave lens is used to reduce the proportions of an object while providing a wider view of the object or area.

Concave and Convex Lens

We find the application of concave lens in treating vision issues and for that, we find the uses of a concave lens in daily life; let’s understand how:

A concave lens is used to treat myopia because the lens diverges the parallel light rays coming from distant objects. Therefore, a virtual image forms at a distant point of the myopic eye. 

Now, that the light rays are at the proper distance, the objects can be easily focused onto the lens, and a clear image is thus formed on the retina.

Below is the diagram to illustrate one of the concave lens examples on myopic eye-correctness (nearsightedness):

Convex Lens

A person who can view far objects clearly, but when it comes to viewing nearby objects, he/she fails to get a clear vision; let us understand what is the use of convex lenses here?

If a person is hypermetropic, the image of a nearby object forms behind the retina. This means that light is focused too far back in the eye that causes things that are close up to appear blurred.

At this moment, a convex lens works as a gold mine for people dealing with farsightedness. 

When a ray of light comes from the distant source is reaching the retina, before it reaches, the convex lens converges and works as a pathway for these rays to converge on the retina.

Below is the diagram to illustrate one of the convex lenses examples:

Now, let’s understand what are the uses of a concave lens followed by a convex lens, and also understand the 5 uses of concave and convex lenses.

Uses of Concave and Convex Lens

So, we will first start with the uses of concave lens Class 10:

We find many uses of a concave lens in daily life, the first two uses of the concave lens are:

A concave lens works as a safety factor for driving at night. This lens diverges the light to far distances that help in a clear view of the far vehicles at night.

We find a small lens fixed in the middle of our doors to view who ranged our doorbell, yes, these are the peepholes to peep who is outside the door. Here, the concave lens gives us a panoramic view of the person standing just opposite the door.

The Rest Three Uses of Concave Lens are:

Various devices like scanners, medical equipment, and CD and DVD players use laser beams. Since laser beams are highly-focused and we use small concave lenses to widen the laser beam to sharply access a specific area.

(About it, we have discussed in the above text on nearsightedness).

Uses of Convex Lenses

When the rays enter the convex lens of the magnifying glass, these rays focus on a specific focal point at the center of it.

(About this, we discussed in the above text on farsightedness).

Most of the cameras that we use have convex lenses, while a few have concave lenses.

Convex lenses help focus on the image well and magnify these at the same time.

Convex lenses are also called microscopic lenses. 

A simple microscope usually has three lenses, out of which, one (convex lens) produces an inverted and magnified image of microorganisms like bacteria, amoeba, etc.

Convex lenses are widely used for multi-junction electric cell. The lens is added above the Fresnel lens to increase the output power of the setup and retrieve the requirement for the employment of solar trackers. 

Interesting Fact

In cameras, we find the uses of a concave and convex lens to get clear images in photography.

To ameliorate the quality of photographs, camera manufacturers use combinations of convex and concave lenses. Here, a convex lens is used as the primary lens of a camera that causes distortions in the photos, which is called chromatic aberrations. Combining both concave and convex lenses eliminates these undesirable effects.