Permanent magnet

In this article we will learn about the permanent magnet. we know application of permanent magnet and their property.

Permanent magnet

Permanent magnets are made of hard magnetic materials like steel. The magnetic material is magnetized during its manufacturing process by subjecting the material to a strong inductive field. Cobalt steel, which is generally used for permanent magnets, is able to retain its magnetism for a long time magnetization because of its greater retentively. Soft iron will only make a temporary magnet and will lose its magnetism easily. Certain alloys of steel particularly alnico (alloy of aluminum, nickel, iron and cobalt with a percentage of copper and titanium) is used for making good grade commercial magnets.
permanent magnet, application of permanent magnet, working of permanent magnet

Permanent magnets are normally made in the form of bar magnets, or as horse-shoe magnets. These can also be made in other shapes to suit special purposes.
When in storage a piece of soft iron called a keeper is put across the two poles as in fig. a keeper forms a closed magnetic circuit with the magnet and helps retain the strength of the magnet over a long period by preventing any external magnetic field from inducing opposite polarities in the permanent magnet and thereby weakening its strength.

Application of permanent magnet

Permanent magnets are a vital part of modern life. They are found in or used to produce almost every modern convenience today, from speakers in mobile phones to the electric motors.

Permanent magnets are used in the following major groups: acoustic transducers, motors and generators, magneto mechanical devices and magnetic field and imaging systems, you will find permanent magnets in many products, such as televisions, telephones, computers, audio systems, air conditioners, washing machines and automobiles.

permanent magnet, application of permanent magnet, working of permanent magnet

hence it is application of permanent magnet if you will find any incorrect above please comment below in comment box.

if you want to know more about the permanent magnet and their application you must watch this video.

Difference between Electric field and Magnetic field


In this article we will know about the difference between electric field and magnetic field. We will also know about electromotive force. Now we will know about electromotive force.

Electromotive Force

Electromotive force (EMF) drives a current of electrical circuits, magneto motive force (MMF) drives magnetic flux through magnetic circuits. The term magneto motive force, though, is a misnomer since it is not a force nor is anything moving. It is perhaps better to call it simply MMF. In analogy to the definition of EMF, the magnetic motive force around a closed loop.

Difference between Electric field and Magnetic field 

These are some difference between electric field and magnetic field which are given below.
difference between electric field and magnetic field , what is basic difference between magnetic field and electric field

            Electric Field

               Magnetic Field

1. In an electric field  the current actually flow , there is movement of electron

Due to MMF flux gets established and does not flow in the sense in which current flows.
2. There are many materials which can be used as insulators that are air, P.V.C synthetic resin etc. form which current cannot pass.

There is no magnetic insulator as flux can pass through all the material, even though the air as well.
3. Energy must be supplied for an electric field to maintain the flow of electric current.

Energy is required to create the magnetic flux, but is not required to maintain it.
4. Electric lines of flux are not closed. They start from positive charge and end on negative charge.
Magnetic lines of flux are closed lines. They flow from N pole to S pole externally while S pole to N pole internally

5. Electric Field (EMF = Current x Resistance)

Magnetic Field ( MMF = Current x Reluctance )
6. There is continuous consumption of electrical energy.

Energy is required to create the magnetic flux and not to maintain it.
7. EMF is the driving force in electric circuit, the unit is volts.

MMF is the driving force in the magnetic circuit, the unit of which is ampere turns.
8. Kirchhoff”s current and and voltage law is applicable to the electric field and circuit.
Kirchhoff”s MMF law and flux law is applicable to the magnetic field and magnetic circuit. it is basic difference between electric field and magnetic field.
9. The flow of electrons decides the current in conductor.

The number of magnetic lines of force decides the flux.

Hence it is the difference between electric field and magnetic field if you will find any incorrect above article please comment below in comment box.

For knowing more about the difference between electric field and magnetic field you must watch this video.

Difference between latch and flip-flop

In this article we will learn about the difference between latch and flip flop and their types. We will know about what is basic difference between latch and flip-flop.

Difference between latch and flip-flop

difference between flip-flop and latch, what is difference betwen latch and flip-flop






Introduction of latch

A latch is an example of a bystable multi vibrator, that is, a device with exactly two stable states. These states are high-output and low-output.  A latch has a feedback path, so information can be retained by the device. Therefore, latches can be memory devices and be store one bit of data for as long as the device is powered. AS the name suggests, latches are used to “latch onto” information and hold in place. Latches are very similar to flip-flops, but are not synchronizes devices and do not operate on clock edges as flip-flop do.

Introduction of flip flop

difference between flip-flop and latch, what is difference betwen latch and flip-flop


A flip flop is a device  very similar to latch in that it is a bistable multi vibrator having two states and  a feedback path that allow it to store a bit of information. The difference between latch and flip-flop is that a latch is asynchronous and the outputs can change as soon as the input does (or at least after a small propagation delay). A flip-flop , on the other hand, is edge-triggered and only changes state when a control signal goes from high to low or low to high. This destination is relatively recent and is not formal, with many authorities still referring to flip-flops as latches and vice versa, but it is a helpful distinction to make for the sake of clarity.

Types of Flip-Flop

A flip flop can maintain in a binary state indefinitely until directed by an input signal to switch states. The most common types of flip flops are discussed below.

Hence it is the difference between latch and flip-flop. If you will find any incorrect above please comment below in comment box.

For knowing more about the difference between latch and flip-flop

Difference between CT and PT

In this article we will learn about the difference between CT and PT. We will also learn about the current transformer and potential transformer. We will know about what is basic difference between CT and PT.
These are some basic difference between CT and PT

 Current transformer (C.T.)

Difference between ct and pt. what is main difference between ct and pt, ct and pt difference

 The current transformer is a step-up transformer which is used to steps down the current to a known ratio. Its primary consists of one or more turns of thick wire in the series with the line. The secondary consists of a large number of turns of fine wire and provides for the measuring instruments and relays a current which is a constant fraction of the current in the line. It is used for measure high current. Which means it is used as current measuring instrument... as like 100/5A rating current transformer.


Potential transformer. 


Difference between ct and pt. what is main difference between ct and pt, ct and pt difference

It is also a step down transformer and steps down the voltage to a known ratio. Its primary consists of a large number of turns of fine wire connected across the line. As like 11KV/110V potential transformer.

Difference between CT and PT


CT (Current Transformer)
PT ( Potential Transformer )
1. It is connected in series with the power circuit. Which means CT is always connect in series with power circuit.
It is connected in parallel with the power circuit. so it is main difference between ct and pt.
2.  its secondary is connected to Ammeter
Its Secondary is connected to Voltmeter
3. Its secondary work always in short circuit condition.
Its secondary work always in open circuit condition so these are also a basic difference between ct and pt.
4. CT primary current depend on power circuit current. Its change according to power circuit current.
PT primary current depend on Secondary burden. According to secondary turn its change.
5. CT primary current and excitation vary over wide range with change of power circuit current.
PT primary current and excitation are restricted to a small range.
6. In this transformer one terminal of secondary is earthed to avoid the insulation break down.
In this transformer one terminal of secondary can be earthed for safety. not compulsory

7. Its secondary never be open circuited. Which means its cannot be open.
Its secondary can be open. Or we can used its in case of open circuit condition.

Hence it is the basic difference between CT and PT. if you will find any incorrect above please comment below in comment box.


Difference between ct and pt. what is main difference between ct and pt, ct and pt difference
For knowing more about the difference between CT and PT you must watch this video.

Measurement Of Flow

In this article we will discus about the measurement of flow. We will learn that how to measurement of flow .

Measurement of Flow

measurment of flow, venturimeter , how to measure of flow , flow measurment
Flow has been an important parameter for measurement in industry and also in the biomedical applications such as blood flow measurement. Fluid can be of different types, like it may be clear or opaque, clean or dirty, wet or dry, erosive or corrosive. The stream of fluid may be multiphase vapor, liquid or slurry, also the fluid may have turbulent or laminar flow, so , different measurement techniques has to be adopted for different types of fluid flows.

1. Laminar Flow

It is a type of measurement of flow

measurment of flow, venturimeter , how to measure of flow , flow measurment

When the fluid is flowing through the conduit at very low velocities, the motion of the individual particles are usually along the lines which are parallel to the conduit walls. The velocity of the fluid profile thus obtained is greatest at the centre of the conduit and decreases outwards ( near the wall). This smooth flow of fluid layers one over the above is termed as the laminar flow.

2. Turbulent Flow

It is also a type of measurement of flow.
measurment of flow, venturimeter , how to measure of flow , flow measurment

When the Flow velocity of the fluid is increased more than the critical velocity, then the fluid profile no longer remain linear but show a random motion which is called as the turbulent flow.

3. Variable Head flow meter

These types of meters are the obstruction type meters as they are placed in between the path of the fluid and hence, puts restriction in the passage of fluid. A differential pressure or head is created across the restriction and this differential pressure is a measure of the fluid flow. The commonly used obstruction meters are the ventury, the flow nozzle and the orifice.

4. Venturimeter

It is a mechanical device which used to measurement of flow.

measurment of flow, venturimeter , how to measure of flow , flow measurment

The Venturimeter is a device which is used for the measurement of discharge through a pipe. It is a short pipe that first tapers to a small cross-section known as throat. The diameter is then again gradually increased to its original size,as shown in figure.

Advantages of Venturimeter

1. They have low head loss about 10% of the differential pressure head.
2. They have a high coefficient of discharge ( 0.95 to 0.97) on account of low loss. Hence they can be used to measure high flow rates in the pipes having diameter of the order of few meters.

Disadvantages of Venturimeter

1. They have large size which renders them unsuitable for application, where space is less.
2. Their cost is high due to their large size, also the cost of installation is high.
Hence it is the measurement of flow if you will find any incorrect above please comment below in comment box.

For knowing more about the measurement of flow you must watch this video.

Working Of Inverter

In this article we learn about the main working of inverter. we will know about what is working of inverter.

Introduction of Inverter

An inverter is used to produce an uninterrupted 220V or 110V AC (depending on the line voltage of a particular country) supply to the device connected as the load at the output socket. The inverter gives constant AC voltage at its output socket when the AC mains power supply is not available.
working of inverter, inverter working , how to work inverter

Working of Inverter

The working of inverter can be considered in the following conditions.

1. When the AC mains power supply is available

When the AC mains supply is available, the AC mains sensor senses it and the supply goes to the relay and battery charging sections of the inverter. AC main sensor activates a relay and this relay will directly pass the AC mains supply to the output socket. The load will be driven by the line voltage in this situation.
Also the line voltage is given to the battery charging section where the line voltage is converted to a DC section where the line voltages is converted to a DC voltage (12 V DC or 24 V DC usually).  Then regulated and battery is charged, using it.
There are special circuits for sensing the battery voltage and when the battery is fully charged this charging is stopped. In some inverters, there will be a trickle charging circuit which keeps the battery constantly at full charge.

2. When the AC main power supply is not available, then the working of inverter

When the AC mains power supply is not available, an oscillator circuit inside the inverter produces a 50HZ MOS drive signal. This MOS drive signal will amplify by the driver section and sent to the output section. MOSFET,S  or transistors are used for the switching operations. These MOSFETs are used for the switching operations. These MOSFET s or transistors are connected to the primary winding of the inverter transformer.
When these switching devices receive the MOS drive signal from the inverter circuit, they start switching between ON and OFF states at a rate of 50HZ. This switching action of the MOSFETs or transistors causes a 50HZ current to the primary of the inverter transformer.  This result in a 220V AC or 110V AC (depending on the winding ratio of the inverter transformer) at the secondary or the inverter transformer. This secondary voltage is made available at the output socket of the inverter transformer. This secondary voltage is made available at the output socket of the inverter by a changeover relay.
Hence it is the working of inverter if you will find any incorrect in above article please comment below in comment box.


working of inverter, inverter working , how to work inverter

For knowing more about the working of inverter you must watch this video.

Passive Electronic Component

In this article we will disscuss about passive electronic component . we will also learn about the active component.

Active and passive component

Those components which required external sources to their operation are called active components. Diode, transistor, SCR, FET Etc. are the some example of active components.

Passive electronic component 

Passive electronic components are the basic building block of some AC circuit like R-L, R-C,R-L-C and these circuit produce resonance so the passive components resistors, capacitors and inductors along with their circuits will be studied in this chapter.

1. Resistor 

Generally, materials have a characteristic behavior of resisting the flow of electric charge or current. This physical properly or ability to resist is known as resistance and is represented by the symbol R. thus , resistance R  of an element denotes its ability  to resist the flow of electric current. It is measured in ohm.
passive electronic component, type of passive electronic component, active electronic component

The element which resists the flow of electric current is called resistor. Resistence forms  a part of almost all the electrical/electronic appliances. It can be used in fan regulator, voltage regulator of DC generator, DC circuit of fluorescent tube, neon-tester, etc. Resistor controls the flow of current by resisting its flow and hence, voltage drop is produced across the resistor.

2. Capacitor 

A Capacitor is a passive electronic components designed to store energy in the electrical field. Besides, resisters, capacitor are the most common electrical component. Capacitors are used extensively in electronics, communications, computers and power systems. A capacitor consists of two conducting plates separated by an insulator (dielectric).
passive electronic component, type of passive electronic component, active electronic component
The storing charge capability is produced by the two conductor plates separated by a distance d and insulator in between them.
Therefore, the three factors determine the value of the capacitance.

1. The surface area of the plate 

The larger the area, the greater the capacitance.

2. The space between plates 

The smaller the spacing, the greater the capacitance.

3. The permittivity of the material

The higher the permittivity, the greater the capacitance.

3. Inductors

 (it is also a passive electronic component)
An inductor is a passive electronic component designed to store energy in its magnetic field .Inductors find numerous applications in electronic and power systems. They are used in power supplies, transformers, radios, TVs, radars and electric motors.

passive electronic component, type of passive electronic component, active electronic component

Any conductor of electric current has inductive properties and may be regarded as an inductor. But in order to enhance the inductive effect; a practical inductor is usually formed into a cylindrical coil with many turns of conducting wire as shown in the figer.
Inductance is the property whereby an inductor exhibits opposition to the change of current flowing through it. It is measured in henry.

Hence it is the basic passive electronic component if you will find any incorrect above please comment below in comment box.

For knowing more about the passive electronic component you must watch this video.

Types Of Connectors

In this article we will learn about the types of connectors. We will know about how many types of connector which are used to connect two connector.

Types of Connectors

Types of connectors, connectors types,working of connectors , how many types of connector

Introduction of Connectors

For knowing types of connector we need to know introduction of connector.
A connector is an electromechanically device used for joining electrical circuits as an interface using a mechanical assembly.
There are  various types of connectors are following.

1. Male/Female type DB Connectors

A D-sub contains two or more parallel rows of pins or sockets usually surrounded by D-shaped metal shield that provides mechanical support, ensures correct orientation, and may screen against electromagnetic interference.

A. Male Connector

The part containing pin contacts is called the male connector or plug.

B. Female Connector

The part containing socket contacts is called the female connector or socket.

1. The sockets shield fits tightly inside the plugs shield.

2. panel mounted connectors usually have threaded nuts that accept screws on the cable and connector cover  that are used for locking  the connectors together and offering mechanical strain relief.

3. Occasionally the nuts may be found on a cable end connector if it is expected to connect to another cable end.

4. When screen cable are used, cable are used, the shield are connected to the overall screens of the cables. This creates an electrically continuous screen covering the whole cable and connector system.

2. Servo 0.1” Connector

In the electronics industry, connectors are most commonly referred to by the spacing between contacts. The most popular size, without a doubt, is the 0.1” connector. It is main types of connectors
Open up any computer and you will find tons of 0.1” connectors from IDE cables to USB and fire wire headers. That’s exactly the type of connector used by the RC industry for servo and anything else that plugs into you receiver. 0.1” connector applies to servo connectors and vice-versa.

3. RCA Connector

A RCA connector, sometimes called a phono connector or cinch connector, is a type of electrical connector commonly used to carry audio and video signals. The RCA connectors are also sometimes casually referred to as A/V (audio/ video) jacks. The name of RCA derives frame the Radio Corporation of America.

4. BNC connector

Types of connectors, connectors types,working of connectors , how many types of connector

The BNC (Bayonet Ne ill-councilman) connector is miniature quick connect/disconnect radio frequency connector used for coaxial cable. If features two bayonet lugs on the female connector, mating is fully achieved with a quarter turn of the coupling nut.it is also main types of connectors.

5. HDMI Connector (high definition multimedia interface)

HDMI is a compact audio/video interface for transferring uncompressed video data and compressed or uncompressed digital audio data from a HDMI compliant source device. Such as a display controller, to a compatible computer monitor, video projector, digital television or digital audio device.
There are some more types of connector which is given below.

6. Audio \ Video connector

Audio connector and video connectors are electrical connector (or optical connector) for carrying audio signal and video signal of either analog or digital format.

7. DIN Connector

A DIN connector is connector that was originally standardized by the detaches institute for norming (DIN).

8. XLR Connector

XLR connector plugs and sockets are used mostly in professional audio and video electronics cabling applications. XLR connectors are also known as cannon plugs. They are used for analog or digital balanced audio with a balanced line.

9. Mini-DIN connector

The mini- DIN connector is a family of multi-pin electrical connectors used in a variedty of applications. Mini DOM is similar to larger odder DIN connector.

10. RF Connector

A coaxial RF connector (radio frequency connector) is an electrical connector designed to work at radio frequencies in the multi megahertz range.

11. USB Connector

A universal serial bus (USB) connector is a connector between a computer and a peripheral device such as a printer, monitor, scanner mouse or keyboard. It is a part of the USB interface, which includes types of parts, cables and connectors.
Hence it is the types of connector if you will find any incorrect above please comment below in comment box.
Types of connectors, connectors types,working of connectors , how many types of connector

For knowing more about the types of connectors you must watch this video.

Electromagnetic induction

In this article we will learn about the electromagnetic induction, we will also know about the right hand rule, left hand rule, helix rule . 

Electromagnetic induction

Whenever a conductor cuts the magnetic lines of forces, then an EMF is induced in the conductor. This is called electromagnetic induction. Thus, electromagnetic induction. Thus, electromagnetic induction is the phenomenon of production of electric current (or EMF) in a coil, when the magnetic flux linked with the coil is changed.

Electromagnetic induction, faraday law of electromagnetic induction, right hand rule, left hand rule

This principle was given by Michael  Faraday and is used in DC generators.
The two law given the basic electromagnetic induction are discussed below.
Faraday’s Law of Electromagnetic induction
Electromagnetic induction, faraday law of electromagnetic induction, right hand rule, left hand rule
With reference to electromagnetic induction, Michael Faraday has given two laws,
They are as follows.

First Law of electromagnetic induction

Whenever the value of magnetic flux passing through any conductor gets changed, then an EMF  is generated in the conductor and this EMF generated is retained until the value of flux is variable.

Second Law Of Electromagnetic induction

The induce EMF , in any closed circuit is equal to the time rate of change of magnetic flux linkage with the circuit.

LenZ’s Law of Electromagnetic Induction

This law gives the direction of induced emf/current. According to this law,
“ the direction of induced EMF or induced current in a circuit is such as to oppose the change in magnetic flux flux which produces it”.

Electromagnetism

Out of three effects ( that is heating, chemical and magnetic) of electric current, one is magnetic effect of electric current. In the year 1819, scientist named orested propounded that, if a magnetic needle is placed near a wire carrying current then the needle is affected by electric current or in other words, a current carrying conductor produces magnetic field.
In this way, the magnetic field produced by a current carrying conductor is called as electromagnetism.
The magnetic filed produced by different types of current carrying conductors are given below.

Magnetic filed of Current Carrying Straight Conductor

Electromagnetic induction, faraday law of electromagnetic induction, right hand rule, left hand rule
The magnetic field around a  current carrying straight  conductor is concentric magnetic lines around the conductor. The center of magnetic lines are produced along the complete length of the conductor.

The direction of electric lines of forces can be found by following two methods.

Right Hand Rule

Electromagnetic induction, faraday law of electromagnetic induction, right hand rule, left hand rule

According to this rule, hold the current carrying conductor in the right hand such  that the thumb pointing in the direction of current and parallel to the conductor, then curled fingers point in the direction of magnetic field or flux around it.

Cork Screw Rule

Imagine a right handed screw to be along the conductor carrying current with its axis parallel to the conductor and tip pointing in the direction of the current flow.
Then, the direction of magnetic filed is given by the direction in which the screw must be turned so as to advance in the direction of the current.

Magnetic Field of a current carrying Loop

Magnetic field in a current carrying conductor is also made of concentric spherical magnetic lines.
The difference is that, inside the loop, these electric lines are concentrated and outside the loop, they are at some distance from each other.

Magnetic Field of a Current carrying solenoid

For know better about the electromagnetic induction we need to know about the magnetic field in circuit or coil.

The magnetic field of a current carrying solenoid or a coil is similar to the magnetic field of  a bar magnet.
One end of solenoid works as a north pole and other end as south pole.
Electromagnetic induction, faraday law of electromagnetic induction, right hand rule, left hand rule
The poles of a solenoid can be pointed out by any of the following rules.

Helix Rule

According to this rule, if the solenoid is held in such a way that curled fingers represent the direction of current, then right hand thumb or outer stretched points towards North pole.

End Rule

If on observing, we find from one pole, the direction of solenoid current is clockwise then, that pole is south pole and if current direction is anti-clockwise then it is north pole.

Hence it is the Faraday law of electromagnetic induction if you will find any incorrect above please you must comment below in comment box


For knowing more about the Faraday law of electromagnetic induction you must watch this video.


Application of Multimeter


In this article we will learn about the application of multimeter. We will learn that where we can use of multimeter. we also studied about the precaution of multimeter.

application of multimeter, multimeter application, precaution of multimeter during application

Application of Multimeter

1. Resistance measuring

2. Measuring of Direct current and voltage

3. Measuring the AC Voltage
These are some application of multimeter which detail given below.

1. Resistance measuring

It is main application of multimeter.  It is used for measuring resistance of circuit.
In resistance measuring, black testing lead is connected with common plug socket and red lead is connected with 10ohm plug socket. After connecting both leads, their point ends short circuited and pointer is adjusted to 0 with the help of zero adjusting knobs.

Now both the ends of unknown resistor are connected with the end points of connecting leads. The résistance of the unknown resistor will be shown on the meter screen. If pointer shows resistor greater than 10 ohm, then red lead is connected with 1mega ohm range plug socket. Repeat above given process to measure unknown resistance.

2. Measuring the Direct Current and Voltage

It is also most important application of multimeter .

When a Direct Current (DC) is passed through the coil of multimeter , the multimeter shows a deflection promotional to DC. For measuring DC current , the multimeter is connected in series with the circuit and to measure DC voltage, it is connected in parallel with the two ends across which the DC voltage is to be measured.
application of multimeter, multimeter application, precaution of multimeter during application

After making connection of multimeter in a circuit, the black lead is connected with negative terminal and red lead with the positive terminal of the battery. The pointer of the multimeter shows the value of DC voltage. In order to measure the DC current, first the function switch is adjusting to the DC current measurement.

Thereafter, the red and black leads of the multimeter are connected with the positive and negative terminal of the battery, respectively. The pointer of the multimeter showed the value of DC current.

3. Measuring of AC Voltage

It is main application of multimeter because its maximum use to measuring of AC voltage in practical life.
In order to measure the AC voltage, the root mean square (RMS) values of voltage is measured with proper setting of voltage. To measure the AC voltage. First the AC voltage is step down upto 6V by using step-down transformer and the multimeter is connected to the two ends of the secondary coil of step-down transformer.

By adjusting the sliding contact Z of rheostat in between X and Y ends, the multimeter readings for AC voltage drop across the resistor are noted.
These are application of multimeter

Advantage of multimeter

After studied the application of millimeter we need to know about the advantage of multimeter.
application of multimeter, multimeter application, precaution of multimeter during application

1. The accuracy is very high.

2. Input impudence is very high hence, there is no loading effect.

3. An unambiguous reading at greater viewing distances is obtained.


4. The output available is electrical which can be used for interfacing with external equipment.

5. Due to improvement in the integrated technology, the prices are going down hence, it became cheaper.

Disadvantage

The requirement of power supply electric noise and isolation problems are the limitations.

Precautions of multimeter  ( during application of multimeter)


1. Before the using the multimeter, the ends of the probes shold be cleaned to remove the insulation deposited on them.

2. Do not connect the multimeter with an AC circuit, as is cannot measure the AC quantity directly.

application of multimeter, multimeter application, precaution of multimeter during application
3. While measuring the current and voltage, set the selector switch at the highest range, then it is reduced to low as per the requirement.

4. If the value of the resistance of a resistor is to be measured, then the resistor should be dismantled from the circuit and power supply is disconnected from the multimeter. Then, the resistance value should be measured.

5. Do not use the multimeter for the measurement of current larger value than the range shown on the rotary selector.

6.  Before using the multimeter, ensure that pointer is set at zero position after touching both the probes together. If it is not so, then adjust the potentiometer to set the pointer ses at zero position. .  So these are precaution which we follow during used of multimeter or application of multimeter.

Hence it is the application of multimeter if you will find any incorrect above please you must comment below in comment box.

If you want to know more about the application of multimeter you must watch this video.