Category: Physics Notes PPT

Carlos Force 

The effect of Coriolis describes the pattern which is of deflection taken by an object which is not firmly connected to the ground as they travel very long distances around  the planet Earth. The effect of Coriolis is responsible for many large-scale patterns of weather.

The key factor which is to note the effect of Coriolis lies in rotation of Earth’s rotation. Specifically if we talk about the planet earth rotates which is faster at the Equator than it does at the poles. The planet Earth is more wider at the area of Equator so to make a full rotation in one period of 24-hour, the region of equatorial race nearly around 1,600 kilometers that is 1,000 miles per hour. If we talk about the near the poles that is planet Earth which rotates at a sluggish that is 0.00008 kilometers that is again 0.00005 miles per hour.

Let’s now pretend that we are standing in the region of the equator and we want to throw a ball to our friend in the middle of the place which is North America. Now let us assume or pretend that we are standing at the North Pole. When we throw a ball to our friend it will again and again appear to land to the right of where he is standing. But this time we will notice that it is because he is moving faster than you are so we have to move ahead of the ball.

Now, everywhere we play a global-scale that really catches in the hemisphere which is the Northern Hemisphere the ball will deflect to the right.

This totally appears to us as the process of  deflection that is in the Coriolis effect. The travelling fluids which are across very large areas, for example, such as air currents, are like the path which is of the ball. They totally appear to bend to the right side in the Northern Hemisphere. The effect of Coriolis behaves the opposite way as in the Southern Hemisphere where we can find that the currents appear to bend to the left side.

The coriolis effect impact is most significant with high speeds or even we can say the long distances. 

Coriolis Effects Meaning

In a subject like Physics or the force of Coriolis is an inertial or we can also say the fictitious force that acts on objects that are in motion within a reference of the frame that rotates with respect to an frame which is inertial frame. With reference to the frame with rotation clockwise direction the force which acts to the motions  left of the object. In one way we can again assume that with anticlockwise or use the word counterclockwise rotation process the force acts to the right direction. The process of Deflection of an object which is due to the force of Coriolis is called the effect of Coriolis. 

Though we can easily recognize previously by others means also that the expression which was a mathematical expression for the force of Coriolis appeared clearly in an 1835 on a paper by French scientist named Gaspard-Gustave de Coriolis. In connection to all that we have discussed the theory of water wheels is also included into it. In the 20th century earlier the term force of Coriolis began to be used in connection with effect which is known as meteorology.

What is Coriolis Effect?

The laws of Newton which were of motion are described as the motion of an object in an inertial that is the non-accelerating frame of reference. So, when laws of Newton’s are transformed to frames which are rotating of reference. At that time the effect of Coriolis and acceleration of centrifugal force appear. When these all things are applied to objects which are massive, then the forces which are respective are proportional to the masses of all of them. The effect of force of Coriolis is proportional to the rate of rotation and the centrifugal force is proportional to the square of the rotation rate. 

The force which is centrifugal force in nature that acts outwards in the direction of radial direction and it is said to be proportional to the distance of the body from the axis of the frame which is rotating. These forces which are additional are termed as the force of inertial that is the force which is fictitious or pseudo forces. By the accounting which is for the rotation by the process of addition of these forces fictitious. The laws of Newton’s motion that can be applied to a system of rotating as though it was an system which is inertial. They are the factors which are corrected which are not required in a system of non rotating.

Corolies Meaning 

In 1651 the scientist who is Italian Giovanni Battista Riccioli and his assistant Francesco Maria Grimaldi who described the effect in connection with artillery in Almagestum Novum that is writing that rotation of the planet Earth that should cause a cannonball fired to the north to deflect to the side of east.That  aimed toward one of the poles of the planet. The Riccioli and the Grimaldi, and Declares that all described the effect as part of an argument which is against the system of heliocentricity of Copernicus. 

In other words, we can say that  they argued that the planet Earth’s rotation should create the effect. And so the failure to detect the coriolis effect was evidence for an earth which is immobile. In 1749 the acceleration of Coriolis equation was derived by Euler and the effect of corolies was described in the equation which is tidal equations of Pierre-Simon Laplace in 1778.

Curie’s Constant, unlike the others, is dependent on the material property that can relate a material’s magnetic susceptibility to its temperature. This was first derived by a physicist named- Marie Curie.

Curie’s law states that the magnetization in a paramagnetic material is directly proportional to the applied magnetic field.

For eg., if we heat any object, its magnetization is said to be inversely proportional to the temperature.

Curie’s Temperature is the temperature at which a ferromagnetic substance or material changes into a paramagnetic substance or material on heating it. This transition is used in the storage of optical media for erasing and inserting new data.

Talking about the physical significance of the Curies constant depends on the effective moments of the ions and hence must be some measures of it. However, it is the same average moment of solid.it is the measure of how strongly a material can sustain magnetic alignment despite thermal fluctuations.

What is Curie Weiss Law?

Before proceeding to talk about Curie’s Constant in detail, let us first see what the Curie Weiss law is all about. This law is considered to be one of the pillars of electromagnetism in physics. It intends to calculate the magnetic susceptibility χ or eta of a ferromagnet in the region of paramagnetism that is present above the Curie point. 

Similarly, we can also say that the susceptibility of any given paramagnetic substance is inversely proportional to the excess of its temperature above the Curie point. Below this temperature, the substance stops behaving like a paramagnet. 

What is a Curie?

The Curie is named after the renowned French physicists Pierre and Marie Curie. To put it simply, it is a unit that is used to measure radioactive activity. The unit’s value is 3.7 x 10^10 disintegrations per second. The original definition of a Curie states that it is ‘the quantity or mass of radium emanation in equilibrium with one gram of radium.’ Another similar unit of measuring radioactivity is the becquerel. In 1975, a committee meeting was chaired in which the becquerel replaced the Curie as the official radiation unit in the International System of Units (SI).

Curies Constant Represented in SI Unit Form 

C = μ0 μB2 ng2 J( J + 1 )/ 3 kB

Here n= number of magnetic atoms per unit volume

g= lande-g-factor 

j= angular momentum quantum number

Kb = boltzmann’s constant

For a magnetic moment for a two-level system, the formula gets reduced to C = nμ0 μ2 / kB

The expressions in the Gaussian unit are represented as:

C = μB2 ng2 J( J + 1 )/ 3 kBC = n μ2 / kB

The constant is used in Curie’s law which states that magnetization is inversely proportional to temperature for a fixed value of the magnetic field.

M = C B/T

This was discovered by Pierre Curie. The relation between magnetic susceptibility is denoted by X, and magnetization M and applied magnetic field H is almost linear at the low fields then:

X = dM/DH ≈  M/H

This shows that temperature T is inversely related to the magnetization system of non-interacting magnetic moments.

Curies Constant Value

Simply, if we take a cubic lattice there is one atom per unit cell. We now are assuming that each atom carries magnetic moment mu= 2muB with the help of Curies constant we will get that C (that denotes Curies constant) =1.3047 K*A/(T*M).

One of the Very Important Laws in this Topic is Weiss law:

We already know the mathematical representation of the law which is M= C*(B/T). Few terms which help in understanding Curie’s law better:

Ferromagnetism: It is the property by which certain materials can form permanent magnets (like iron)

Magnetic Susceptibility: It is the measurement of how much a substance can get magnetized in a magnetic field.

Paramagnetism: When some materials get attracted by the external magnetic field, then this situation is known as paramagnetism.

Permeability: It measures the ability of a substance to support the formation of magnetic fields within itself.

Curie’s Point: It is the point or temperature above which certain substances lose their permanent magnetic property.

Curious Constant: As discussed, it’s the property depending upon the material that relates to materials’ magnetic susceptibility and temperature.

Curies Weiss Law: It informs us about the magnetic susceptibility that is denoted by the letter X of a ferromagnet in the paramagnetic region above the Curies point; it is denoted as X= C/T-Tc.

C= Curies constant 

T= absolute temperature

Tc = Curie’s Temperature, both measured in kelvin.

Curie’s Constant Unit 

We define the unit of Curies constant as K*A/(T∗m)

The magnetic moment μθ is a characteristic number that describes the magnetic property of a single atom or a particle molecule etc.

We can easily calculate the value of Curie by dividing the decay rate per second by 3.7 x 10^10; the decay rate is equal to 1 Curie. Taking an example of 1 gram of cobalt -60 is equal to 1119 Curie and it is because  4.141 x 10^13/ 3.7 x 10^10 = 1,119 Ci.

Curie’s Temperature for Some Ferromagnetic Substances

Students should note the Curie temperatures of some important substances that are frequently asked in examinations. The list is given below:

Curies Table of Content 

Curie’s Law of Magnetism: States that magnetization that’s M of a paramagnetic substance is directly proportional to the Curies constant which is denoted as C and magnetic field which is denoted as B which is inversely proportional to T that is temperature  writing it in the equation:

M=C/T*B

C- characteristics susceptibility to magnetic fields of paramagnetic materials. It depends on the strength of the atoms which are forming the substances and on the density of these moments.

Limitations of Curie’s Law

There are some failures in these laws like it fails in the Curie’s Weiss law fails to describe the susceptibility of certain materials these and are considered as the behavior in the form 1/T-Tc.

However, at the temperature which is denoted as T,>>Tc the whole expression still holds, however as soon as we replace Tc by temperature which is higher than Curie’s Temperature that C and if T becomes zero, then the susceptibility becomes infinite. 

Sometimes it takes the Weiss constant to distinguish it from the temperature of the Weiss point.

There are a few modifications in these laws: The Weiss law which was for a paramagnetic material that’s written as X = M/H= Mμ0/B= C/T.

Where μ0 is called the permeability of free space.

M is called magnetization B= μ0 is called a magnetic field and C is called the material-specific Curies constant.

The total magnetic field for Curies Weiss law is B + lambda M (lambda = Weiss molecular field constant). It clearly shows that magnetic susceptibility is inversely proportional to temperature.

Which is the Weiss law

X= C/T-Tc

When temperature Tc is Tc= C lambda< /p>

The famous Davisson Germer electron diffraction experiment was performed due to the lack of explanation of an atomic model’s wave nature’s properties. In 1927 scientists C.J. Davisson and L.H. Germer carried out an experiment to explain an electron’s wave nature. This was proposed through electron diffraction method. 

This section discusses the experiment and its observation in a detailed manner. The explanations are lucid in nature to help students understand the concepts better. This topic carries heavy weightage in term of marks in the examination. 

With a thorough reading, students can solve the variables and equations related to Davisson Germer experiment easily.

Davisson and Germer Experiment on Electron Diffraction Result

Under the Davisson Germer electron diffraction experiment, a student can get the value of scattering angle θ. They can also find the possible difference V’s equivalent value at which electrons’ scattering is the highest. The data collected by Davisson and Germer gives two theories or an equation that again shows the same value for λ. If we include De Broglie’s duality in a wave-particle, there can be two equations (a) and (b).

The equation that substantiates the De Broglie’s wave-particle duality is – 

Here one can find V’s value to be 54 V

Now we know that λ = 12.27/√5454 which gives us the value 0.167 nm 

If we go through the equation, we find that’d’ will have a value of 0.092 nm. It is gained through X-ray scattering. That gives us v’s value to be 54 V. The angle of scattering is equal to 500500. 

Now applying this value in a second equation, we get that

Let’s take n’s value to be 1, while λ is 0.165 nm

This value finally verifies the theoretical explanation of the De Broglie equation. 

Davisson and Germer Electron Diffraction Experiment Observation

To find the presence of an electron in a particle form, a student can use a detector. Davisson Germer electron diffraction experiment indicates that a detector receives electronic current, i.e. electron. Here the strength or intensity of an electric current produced or received and scattered in an angle is studied. This current referred to as electron intensity.

Another observation that students can find here explains how the intensity of a scattered electron is never continuous. One can find both minimum and maximum value analogous to the utmost and least diffraction pattern gained via X-rays.

Scattered electrons have continuous intensity levels, which displays a maximum and the least analogous value to the utmost, and minimum value of a diffraction pattern created by X-rays. This value can be found by studying potential differences and scattering angles.

The Setup of Davisson Germer Experiment

Lastly, under this Davisson Germer electron diffraction experiment, a student can understand the setup formed. Ideally, the thought behind this elaborate experiment was the nature of wave particles reflected.

Davisson and Germer’s experiment shows that waves reflected in a Ni crystal that passes two atomic layers contain a constant phase disparity. Students can learn that after reflection, these waves encumber annihilation or construction. This gives rise to the famous diffraction pattern.

It is seen that during the Davisson and Germer experiment, electrons are replaced with wave particles. These electrons combined to form a diffraction pattern. Finally, producing the ultimate result, which is the dual nature of matter.

Davisson Germer experiment electron diffraction chapter is complicated in terms of equation and usage. A student needs to have a clear understanding of the basic topics that carry high marks. This complex topic requires students to depend on guidebooks and study materials that offer only exercises not a valid explanation.

Introduction

In physics, we study the magnetic electric force charge to find out its true nature while observing and researching. We analyze the force exerted into space with a constantly varying flow of current. 

 

The word electromagnetism can be elaborated as the summation of the electric and magnetic force acting simultaneously towards the space due to the motion of charged particles. The forces which are available around us can be studied through electromagnetism.

 

Lorentz transformation is put forward by the Dutch scientist Hendrik Antoon Lorentz. The frame of reference is any kind of that you are measuring something. For example, if you are standing on the floor and looking at some physical event such as a firecracker explosion or collision of two stones. that floor will become your frame of reference. If you are traveling inside the train and looking outside to a physical event, the train will be your frame of reference.

 

What is Lorentz Transformation?

Lorentz transformation can be elaborated as the linear transformation which consists of a rotation of space along with the constant distance between space and time. In physics, we can study Lorentz transformation which comes under linear transformation.

 

Lorentz transformations are a set of equations used in relativity physics to connect the space and time coordinates of two systems moving at the same speed. Lorentz transformations are used to describe extremely fast phenomena that approach the speed of light. They formally describe the relativity ideas of space and time not being absolute, length, time, and mass all being dependent on the observer’s relative motion, and the speed of light in a vacuum being constant and independent of the observer’s or source’s motion. In 1904, a Dutch physicist named Hendrik Antoon Lorentz devised the equations.

 

Lorentz Transformation Derivation

We are using mathematics to elaborate and predict the events that happen in the world. 

In general, an event indicates something that occurs at a given location in space and time. The Lorentz transformation transforms between two reference frames when one is moving with respect to the other. 

 

The Lorentz transformation can be derived as the relationship between the coordinates of a particle in the two inertial frames on the basis of the special theory of relativity.

 

The Lorentz transformations are exclusively related in terms of change in inertial frames. Furthermore, this link is frequently found in special relativity. This transformation is also a type of linear transformation in which mapping occurs between two modules involving vector spaces.

 

The operations of scalar multiplications and additions are preserved throughout linear transformation. Furthermore, this transition has some innate characteristics. An observer moving at a different velocity, for example, could measure event ordering, elapsed periods, and various distances, but the constraint here is that the speed of light should be the same in all inertial frames.

 

Here, 

 

S and S‘  = two inertial frames out of which S‘ is moving relative to S with v velocity along positive x-axis

 

At the beginning t = t‘ = 0

 

Origin O and O’ will coincide

 

Lorentz Transformation Equation Derivation

The wavefront of light emitted at t = 0 when reaches at P, the position and time observed by observers at O and O‘  are ( x, y, z , t ) and  (t‘,  x‘, y‘, z‘)respectively.

 

Time taken to reach O from P as observed in frame S is:

t = [frac{OP}{c}] = [frac{sqrt{x^{2} + y^{2} + z^{2}}}{c}]

or, x[^{2}] + y[^{2}] + z[^{2}] = c[^{2}]t[^{2}]

or, x[^{2}] + y[^{2}] + z[^{2}] – c[^{2}]t[^{2}] = 0

The same equation can be obtained for t‘ time taken by light to reach from O‘ to P,

 x[^{‘2}] + y[^{‘2}] + z[^{‘2}] – c[^{2}]t[^{‘2}] = 0

Since both equations represent the same spherical wavefront in S and S‘ frame, they can be equated as:

x[^{2}] + y[^{2}] + z[^{2}] – c[^{2}]t[^{2}] = x[^{2}] + y[^{2}] + z[^{2}] – c[^{2}]t[^{2}] ………….(1)

Since frame S and S‘ are moving relative to S along the x-axis, length in direction is perpendicular to direction of motion are unaffected.

i.e., y‘ = y and z‘ = z ……….(2)

From (1) and (2), we have  

x[^{2}] – c[^{2}]t[^{2}] = x[^{‘2}] – c[^{2}]t[^{‘2}] (a)

In the frame S

x = v*t

or, x – v*t = 0

Whereas for frame S‘

x‘ = k (x – v*t)   (3)

Since both are relative, we can assume s is moving relatively along with s‘ having a velocity v along the negative x – axis.

So, position of O at any instant of t‘ relative to observer is 

x‘ = – v ∗ t‘

or, x‘ + v ∗ t‘ = 0

Whereas position of O relative to observer O in frame S is x = 0 , so x and x‘ must be related as

x‘ = k‘ (x‘ – v ∗ t‘) (4)

Where, K‘  is another constant

Substituting the value of x‘ from equation 3, we get;

x = [K‘(x – vt) + vt‘]

t‘ = [(kt – [frac{x}{v}])(1 – [frac{1}{k‘}])] (5)

Putting x’ from eq.3 and t’ from eq.5, in eq.(1) we get 

[x^{2} – c^{2}t^{2} = K^{2}(x – vt)^{2} – c^{2}k^2 (t – [frac{x}{v}])(1 – [frac{1}{k‘}])^{2}]

By simplifying and equating coefficient of t² we get

K = [frac{1}{sqrt{1 – frac{v^{2}}{c^{2}}}}] (7)

 Similarly, we get,

K‘ = [frac{1}{sqrt{1 – frac{v^{2}}{c^{2}}}}]

Substituting the value of K and K’ in equation (3) and (5), we get,

x‘ = [frac{1}{sqrt{1 – frac{v^{2}}{c^{2}}}}] (x – vt) and 

t‘ = [frac{1}{sqrt{1 – frac{v^{2}}{c^{2}}}}] (t –  [frac{x}{v}] x  [frac{v^{2}}{c^{2}}])

= = [frac{1}{sqrt{1 – frac{v^{2}}{c^{2}}}}] (t – [frac{vx}{c^{2}}])

The Lorentz transformations are 

x‘ = [frac{1}{sqrt{1 – frac{v^{2}}{c^{2}}}}] (x – vt) ; y‘ = y ; z‘ = z

And t‘ = [frac{1}{sqrt{1 – frac{v^{2}}{c^{2}}}}] (t – [frac{vx}{c^{2}}])

What are the Differences Between Galilean and Lorentz Transformations?

Magnets and magnetic fields produce a classic phenomenon that is known as Magnetism. Its origin is dependent on the orbital movements of the electrons of the element. It might be a surprising fact for you, but every matter has some magnetic property, and the only difference that is there is in respect to the amount of magnetism present. Moreover, the classification of the materials is done based on their magnetic properties.

 

Types of Magnetic Materials

Now, moving on to the classification of a magnet; it happens based on magnetism and goes as follows:

1. Diamagnetism

2. Paramagnetism

3. Ferromagnetism

4. Ferrimagnetism

5. Antiferromagnetism.

The matters showing Paramagnetism and Diamagnetism are the ones that do not exhibit any magnetic interactions. However, the ones in the other three groups show a long-range magnetic order after certain temperature conditions.

Ferromagnetic and Diamagnetic materials are opposite to each other. When the former one shows magnetic behaviour, the latter one does not exhibit any such property.

 

What is Diamagnetism?

Now, how should we define diamagnetic materials?

A diamagnetic material is one that has a very low or minimal magnetic effect due to the absence of any unpaired electrons in them. 

Another way for explaining diamagnetic meaning is through Lenz’s law. It states that diamagnetic materials get induced dipoles in the presence of an external magnetic field, and this happens in such an order that the magnetic field and the induced dipoles repel each other.

 

What is Diamagnetic Material?

Moving on to the substances available globally, what are diamagnetic materials?

In 1845, Michael Faraday discovered diamagnets and the meaning of diamagnetic materials. Further, with the creation of the modern-day periodic table, experts commented and proved that most of the elements are Diamagnetic, like Gold, Silver, Copper, etc. These di-magnetic elements cover the majority of the table, and the other categories have a lesser number of elements. Moreover, semiconductors are the best diamagnetic materials. They also exhibit the diamagnetic field and this perfect diamagnetism in the superconductor is known as the Meissner effect.

 

Diamagnetic Properties

After understanding the diamagnetic definition well, let us move further with the properties. Properties of the diamagnetic materials are:

1. The diamagnetic materials have all the paired electrons, and none of the electrons is the valence, resulting in the absence of atomic dipoles in these materials. This happens because the overall magnetic moment of each atom in the compound cancels out.

2. In the presence of the magnetic field, there is a repulsion between the diamagnetic substance and the magnet.

3. The field weakly repels the substances having diamagnetism; thus in the non-uniform field’s presence, these substances move from the stronger region of the magnetic field to the weaker one.

4. In comparison to the magnetizing field, magnetization intensity is lower in the negative direction, and proportional.

5. Diamagnetic materials have lower and negative magnetic susceptibility.

6. The relative permeability is also a bit lower than unity.

7. The materials that exhibit diamagnetism do not obey Curie’s Law. They are independent of the action of temperature.

8. When suspending a rod of some material following diamagnetic definition in the uniform magnetic field, it comes to rest in the perpendicular direction with respect to the magnetic field. This happens as the magnetic field is highest at the poles.

9. A diamagnetism-exhibiting liquid placed in a U-shaped tube gets depressed in the limb that is in the middle of the magnetic poles.

10. The dipole moment of the di-magnetic substances is lower and in the opposite direction of the magnetic field H.

11. When placing a diamagnetic liquid in a watch glass and then keeping the glass between two poles that stays closely, liquid accumulates at the sides of the glass. The liquid exhibits depression in the middle as the magnetic field is the strongest there.

12. When placing a diamagnetic liquid in a watch glass and then keeping the glass between two poles that stay far apart, liquid accumulates in the middle of the glass. This reaction occurs because the magnetic field is weaker in the centre.

 

Fun Facts on Diamagnetic Substances:

Diamagnetic properties cause the objects to levitate. Unbelievable, right? But this is a proven fact! 

The reason is that the diamagnetic materials get magnetism only in the presence of the magnetic field, and these induced fields are opposite to the acting magnet. This is why they get utilized in many experiments for levitating the objects.

Moreover, even the Maglev train works with the help of this property of diamagnetism. Additionally, once a frog also got levitated in the presence of a strong magnetic field in an experiment.

Ammeter and voltmeter both devices are used in an electrical circuit to measure different aspects of electricity. Among them, an ammeter gives you the measure of current while the voltmeter helps in calculating the voltage or potential difference between two points in an electric circuit. 

What is Ammeter and Voltmeter?

Ammeter – It is an instrument that is used to measure the current in an electrical circuit. It gets its name from Ampere which is the unit of electric current. 

Applications of an Ammeter:

• This device is easily available and helps determine the flow of current quite accurately.

• It can be used both domestically and for industrial purposes. 

• It is widely used by manufacturing and instrumentation companies.

• It can be used with a thermocouple to measure temperature.

• It can be used to check faulty circuits in offices and homes. 

Voltmeter – This instrument measures the voltage between two points in an electrical circuit. It is present in both digital and analogue forms. 

Applications of a Voltmeter

• A voltmeter is used for a number of purposes even though it is not as accurate as an ammeter.

• It measures the voltage in a circuit and is also used in both homes and big factories.

• It proves quite useful in debugging thereby certifying the presence of the optimal value of the required voltage.

• It can be coupled with cathode ray tubes to ensure the accuracy of the results and measurements taken. 

• It is also used in labs by young students and scholars for experimenting and testing purposes.

What is the Difference Between Ammeter and Voltmeter? 

There are two ways to measure electricity 

• Using current 

• Using voltage

Ammeter and voltmeter are used to measure the flow of current and the measure of voltage, respectively. The significant difference between these two devices lies in their use. Further, look at the table below to understand the difference between an ammeter and a voltmeter. 

Mentioned above are a few significant differences between ammeter and voltmeter. Both instruments are present in analogue and digital forms. Analogue meters have a pointer that depicts the measurement whereas digital devices display the value of current or voltage on the screen.  

Galvanometer

We have talked about ammeters and voltmeters but now let’s see what a galvanometer is. It is a device used to detect current flow in a circuit. Current sensitivity is the term used to refer to the current that gives a full-scale deflection of the galvanometer’s needle. Thus, it is the maximum current that the instrument is capable of measuring. A galvanometer can even function as an ammeter or a voltmeter upon making some requisite changes. 

Potentiometer

When we try measuring the EMF of a battery, we generally connect the battery directly to a standard voltmeter as in the case in laboratories. However, this implies that the actual quantity measured by the voltmeter is the terminal voltage V. Voltage is related to the EMF of the battery by the equation V=emf−Ir, where the letter i is used to denote the current that flows in the circuit and r is the internal resistance of the battery. 

A potentiometer is a null measurement device that is also used to measure voltage but in a slightly different manner. A voltage source is connected to a resistor in the circuit, and a constant current is made to pass through it. There is a steady drop in potential along with the wire present. Consequently, a variable potential is obtained through contact along the wire.

Multiple-Choice Questions 

1. Current is measured using _______ by connecting it in _______ with the electric circuit. 

1. Voltmeter, series

2. Voltmeter, parallel

3. Ammeter, series

4. Ammeter, parallel

Ans: c 

2. Digital meters are preferred over analogue meters. 

1. True 

2. False 

Ans: a

3. An ideal voltmeter can be considered as a _________ circuit. 

1. Power

2. Infinite 

3. Short

4. Open 

Ans: d 

4. An ideal ammeter can be treated as a __________ circuit. 

1. Open 

2. Short

3. Infinite 

4. Power

Ans: b