Electromagnetic field dangers and radiations

Electromagnetic field dangers and radiations

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Radiation

Electricity

Each substance is made up of atoms. The original particle positively charged inside the atom is the proton, the negatively charged particle electron and the charged particle particle neutron, the same number of protons and electrons in any object.

If some electrons are ejected from an object, then the number of protons in the object will exceed the number of electrons, this will cause the object to be positively charged. If some electrons are given from outside, then the number of electrons in the object will exceed the number of protons.

This will make the item negative. This made it clear that the primary sources of electric charge are protons and electrons. They remain in the object itself. Only when the electrons in the object decrease or increase, the object is positively charged or negatively charged.

Electro-conductor and insulating material

Electric conductors are possible in materials through which electric charge can pass from one place to another, such as metals, acids, alkalis, aqueous solutions of salts, etc.

All these are examples of electrical conductive substances through which the electric charge cannot pass from one place to another, they are called anti-electric, such as wood, rubber, mica, paper, pure distilled water etc.

But after adding a little acid or alkali to it, it acts like an electric conductor. The electrical resistance of the conductors increases with the increase in heat and its electrical conductivity decreases.

We know that only electrons go out of matter in the oscillation action of substances or come into matter from outside, transfer of some electrons of matter within the substance is called electric conduction. The electrons that can move within a substance are called free electrons of the substance.

Michael Faraday (1791–1867)
Michael Faraday was an experimental physicist. He did not receive any formal education. In the early period of his life, he worked at the bookbinding shop. Faraday used to study books that came to the shop for binding. This led to his interest in science.

He had the opportunity to listen to public lectures of Sir Humphrey Davy, scientist at the Royal Institute. He carefully prepared notes of Dewey’s lectures and sent them to Sir Dewey. He was soon made an assistant in Dewey’s laboratory at the Royal Institute.

Faraday made many revolutionary discoveries, including the laws of electrical magnetic induction and electrical decomposition. Many universities tried to confer honorary degrees on him, but he turned down such honors. Faraday loved his scientific work more than any honor.

In addition to conductors and dielectric materials, there are some substances whose electrical conductivity is between conductor and dielectric material.

Such materials are called semi-conductors, if the heat of the semi-conductor is increased too much or some impurities are added to them, then they work like a conductor. The conductivity of semi-conductive materials increases with increasing heat and decreases with removal of heat. Semi-conductive materials behave like ideal dielectric at absolute zero temperature. Major examples of semi-conductive materials are carbon, germanium, silicon etc.

If the temperature of a metal is reduced, the electrical conduction in it increases, that is, its electrical resistance decreases. The resistance of some metals, when approaching near absolute zero temperature, becomes almost zero and they are then called superconductors.

Charge flow within the wire
How does a metal conduct electricity? You might think that low-energy electrons have a lot of difficulty passing through a solid conduction. The atoms within the solid are clustered with each other and have very little space between them.

But it has been found that electrons travel from an ideal solid crystal without interruption as easily as they would in a vacuum. However, the speed of an electron in a conductor is very different from the speed of charges in a blank space. When a steady current flows through a conduction, the electrons within it move at a fixed average runoff speed.

For a typical copper wire with a small current flowing through it, this runoff can be calculated and is actually found to be very low, mms-1. Then why is it that the light bulb starts lighting when we switch on? It cannot be that the current starts only when an electron moves from one terminal of the power supply to another via the bulb itself, because physical runoff of electrons in a conductor wire is a very slow process.

The exact process of electric current flowing at almost the same speed as the speed of light is fascinating.

Trogester: Trogistors used for radio, television, computer etc. are made from semi-conducting materials.

Integrated Circuit: This is abbreviated as IC. In general, IC is a system of semi-conductive devices that can perform certain types of tasks or perform many tasks, such as the function of a switch, the function of a timer, etc.

Power Sector, Potential and Capacity

Rule of coulom

The force of attraction or repulsion between two stationary charges is directly proportional to the product of the quantities of both charges and inversely proportional to the square of the distance between them and this force acts along the line joining the two charges. If two point charges q1 and q2 are located in vacuum or air at a distance r from each other, according to Coulom’s law, the force exerted between those charges

[latex] F = \ frac {{kq} _ {1} {q} _ {2}} {{r} ^ {2}} [/ latex]

Here k is a constant. Its value is for export or air –

K = 9 × 109 newton-m 2 / coulom 2

Electric field intensity

The force the coulom experiences at any point in the electric field is the positive charge, it is called the intensity or electric field of the electric field at that point.

[latex] E = \ frac {F} {q} [/ latex]

The intensity of the electric field is expressed in newton / coulom and is a vector amount.

Electrical potential

The work done to bring a positive test charge from the end to a point in the electric field and the value of the test charge is called the electric potential of that point. The SI unit of electric potential is volt and the voltage is a scalar.

[latex] V = \ frac {W} {Q} [/ latex]

Voltage: If 1 coulom of work is required to bring 1 coulom positive charge from infinity to a point of electric field, the electric potential of that point is called 1 volt.

Spacing

The work done in moving a coulom positive charge from one point to another point in the electric field is called the potential difference between those points. The unit of voltage is also volt and it is also a scalar.

Power capacity

The capacitance (c) of a driver is called the impedance of the charge (q) given to the driver and the change in the potential of the driver (v) due to that. meaning –

The SI unit of C = q / v is Faraday (F).

Current current

Electric current: The flow rate of electric charge in a conductor is called electric current. The positive charge is considered to be the direction of current.
Power cell: The chemical energy in an electric cell is converted into electrical energy. There are two types of cells – primary and secondary.
The electrical carrying force of the cell: 1 The work done by the cell to make the coulomb charge a full circle in the entire electrical circuit is the work done by the cell or v.v. it is said. The unit of VV is volt.

Potential: When current flows through a cell, the potential difference between its ends is called the voltage of the cell. It is less than VIV.

Internal resistance of the cell: The resistance generated in the path of the current through the electrolyte of the cell is called the internal resistance of the cell.

Lightning conductor: Lightning conductor is between two charged clouds or between charged clouds and earth. A lightning conductor is a pearl copper strip, with several pointed ends made at the top. This pointed end is placed on the top of the buildings and the other end is buried in the ground with a copper strip. When charged clouds pass over the building, their charge is captured by the lightning conductor and this charge is transferred to the ground without any loss. Thus it is used for the protection of buildings.

Hans Christian Orsted (1777–1851)

Hans Christian, one of the leading scientists of the 19th century. Orsted played a pivotal role in understanding electrical magnetism. In 1820 AD, he accidentally discovered that the current in a metal wire produced a deflection in a nearby compass. Based on his observations, Austand proved that electricity and magnetism are interrelated phenomena. His research went ahead with new technologies; Such as radio, television, fiber optics etc. were created. In his honor, the unit of intensity of magnetic field, Orsted has been kept.

Simple circuit

rules of OM

The value of current flowing in a conductor is proportional to the voltage across its ends. Therefore

[latex] V-IR [/ latex]

Where V potential, I current and R is a constant for the conductor in those conditions, called the electrical resistance of the conductor. Hence, express the potential in volts and current in amperes, then the value of resistance will be in volts / amperes. Volt / ampere is called Om.

Omi Resistance

The conductors which follow Ohm’s law are called a resistive and their resistance is an ohmic resistance, such as a manganine coil.

Anomalous resistance

Conductors that do not follow Ohm’s law are called anomie resistors and their resistance is anomie resistance, such as the resistance of a triode valve.

Specific resistance

The electrical resistance between the face-to-face panels of a meter-side of the money for a conducting substance is called the specific resistance of that substance. Its unit is ohm meter. The thicker wire made of the same material has less resistance and the thinner wire has higher resistance, but the specific resistance of both is the same, as it depends only on the nature of the material.

Gradient adjustment of resistors

If the resistors are connected to each other in such a way that the same current flows in them and different resistors have different potentials between them. So this is called a gradual adjustment of resistors.

Parallel sequence adjustment of resistors

If the resistors are combined in such a way that the potential at each resistance remains the same, but the currents in it may also remain uneven, then it is called parallel order adjustment of the resistors.

Effect of heat on resistance

The resistance of pure metal wire increases with heat. Thus resistance can be calculated at a temperature with respect to R = R0. Where a is the heat resistance coefficient of that metal and R0 is the resistance at 0 ° C of that metal.

Electric power

The rate of loss of energy in an electric circuit is called power. Its SI unit is watt. Shakti can be expressed as a formula –

Power = current x potential

And 1 weight = 1 ampere x 1 bolt

Kilowatt-hour unit or unit

A 1 kWh unit or 1 unit is the amount of electrical energy that is spent in a circuit in 1 hour, while a circuit has 1 kilometer of power, so

KWh unit = volt × ampere × hour / 1,000 = watt × hour / 1,000

Electric current effects

Magnetic effect

A magnetic field is generated around each current carrying wire.

Scientist Orsted discovered through an important experiment that if a magnetic needle is placed near a current carrying wire, it deviates, since the magnetic needle can only be distracted by the magnetic field, so it is clear that the electric current is magnetized. Field. This phenomenon is called electromagnetic effect.

Lawrence Force

When a charged particle moves in a magnetic field, a force is applied to it, which is called the Lawrence force. This force is proportional to the charge of the particle, its speed, and the intensity of the magnetic field.

Electromagnet

Parinalika with soft iron core is called electromagnet. They are used in factories, in hospitals, for making electric bells, telecommunication, transformers, dynamos, telephones, etc.

Photometer

A sensing device is the presence of electric current in an electric circuit. In it, a rectangular coil is located between the magnetic poles with the help of two springs. Both ends of the coil are connected by spring with connective leaves. An indicator is also attached to the horoscope, which indicates the presence of a current by rotating on a semicircular scale. Therefore, with the help of this machine, an electric current of 10-6 amperes can be measured.

Ammeter

A shunted thermometer is called ammeter. It has a scale, above which a needle rotates. With its help, the value of current is known in amperes. The resistance of an ideal ammeter is very low. The ammeter is placed in series in the electric circuit.

Shunt use

The shunt protects the thermometer from high currents, as it flows the majority of the main current. The total resistance of the shuttered dielectric is also greatly reduced with the resistance of the shunt reduced.

Voltmeter

A voltmeter is made by placing a high resistance in the series of dielectric. Its scale is calibrated in volts to read the potential between any two points of the circuit.

The resistance of the voltmeter is very high. It is added in parallel order between the two points between which the voltage has to be found.

Electromagnetic induction

If the magnetic flux passing through a closed circuit is changed, then an electric current is generated in the circuit, which is called induced current. An electric current is produced by the change of magnetic flux. Therefore, this phenomenon of generating electric current is called electromagnetic induction.

VBA generated in magnetic flux change Is called the induced electric carrying force. The current induced by the circuit exists as long as the flux change occurs.

Faraday’s laws of electromagnetic induction

First rule: When there is a change in the magnetic flux associated with a coil, an induced electric carrying force is generated in that coil.

Second law: The induced electric carrying force is directly proportional to the rate of change of the magnetic flux.

Inspired World Bank [latex] \ E = N \ frac {\ Delta \ phi} {\ Delta t} [/ latex]

Where N = the number of turns of the coil and [latex] \ frac {\ Delta \ phi} {\ Delta t} [/ latex] = the rate of flux change.

Value of induced current

Induced electric current [latex] \ left (i \ right) = \ frac {e} {R} = \ frac {N} {R} \ left [\ frac {\ Delta \ phi} {\ Delta t} \ right] [/ latex]

Where R = resistance of the circuit.

Value of induced electric charge –

Induced electric charge (q) = i Δr

Lange’s law

The direction of the induced electric carrying force is always such that it opposes the cause from which it originated.

Fleming’s right hand rule

If the thumb, index finger, and middle fingers of the right hand are circulated vertically in such a way that the thumb represents the conductor and the direction of motion, and the index finger shows the direction of the magnetic field, then the middle finger induced v. Will show the direction of the force.

Inspired VVB

At the ends of the dynamic conductor in the magnetic field Is generated. The VB generated at the ends of the conductor in v velocity in the perpendicular direction of the magnetic field B The following formula is derived from –

V = vBL where L is the length of the driver, if v is in meters / second, B is in Weber / m 2 and L is in meters, then the v.v. Will be received in volts.

If the conductor moves along the magnetic field at a beta angle, the induced potential will be V = vBL Sin beta.

Self induction

This is a phenomenon in which the change in the flux resulting from the current is induced in a circuit. Is born The flux corresponding to a rod coil is directly proportional to the current flowing in it. Where L is the constant, which is called the self-induction coefficient or self-inductance of the coil. Its unit is Henry.

Interactive induction

Interaction induction is the phenomenon of changing the current in one coil to generate the induced electric carrying force in the other coil.

Interdependent induction coefficient: The reciprocal inductance between two coils is numerically visible, that induced VVB generated in a coil. Is equal to, which arises due to the rate of change of current in the second coil. Henry is also a reciprocal induction multiplier or unit of reciprocal inductance.

Chemical effect of electric current

An aqueous solution of a salt through which an electric current can pass is called electrolyte.

When an electric current is carried in aqueous solution of a salt, its electrolysis occurs. That is, this solution decomposes into positive and negative ions. This phenomenon is called the chemical effect of electric current. The device in which aqueous solutions of salts undergo electro-decomposition is called a voltmeter.

When an electrolytic salt forms an aqueous solution, the salts are immersed in two types of ions. There are opposite types of charge on those ions. The ions which have positive charge are called cation and the negatively charged ions are called anion.

The positive electron of the voltmeter is called the anode and the negative electrode is the cathode. Electrolysis has many applications in daily life, some of which are important as-

Electroplating

Electroplating is the act of placing the surface of another metal on another metal. The jewelery of cheap metals sold in the market is made valuable by mounting a layer of silver or gold.

For example, in order to make silver fold on copper, an aqueous solution of silver nitred is taken in a voltmeter and the cathode of the copper plate and the anode of the silver plate are taken in it. In aqueous solution, silver nitred breaks down into silver and nitrate ions.

When the electric current is passed, the silver ions begin to accumulate on the copper plate, causing a thin layer of silver to pass over it. Ordinarily, the metal on which the coating is to be made, the cathode and the metal to which it is coated, is made an anode.

Electro-printing

Blocks are made for printing by electrolysis in electro-printing.

Electrical refining of metals

The impure or composite metals are refined by electrolysis. In this method, the mixed metal is taken as anode and its cathode. Both of these are added to an aqueous solution of a metal salt to form a voltmeter and electrically decompose. The metal mixed with the anode dissolves in the solution and the pure metal is collected at the cathode.

Thermal effect

When an electric current is carried in a conductor, the moving electrons continuously collide with the atoms of the conductor and in the process transfer their energy to the conductor atoms. This increases the temperature of the conductor.

This phenomenon of increase in heat of the conductor is called thermal effect of electric current. In this way, electrical energy is converted into thermal energy.

If the resistance of the wire is R ohm and 1 ampere current is flowing in it, then 12R joule of heat will be produced per second wire, which we can also call 0.24 12R calories.

Thermal effects of electric current are used in household appliances such as electric heaters, electric presses, bulbs, tube lights etc.

Electric heater

Electrical heaters are used in many forms. It consists of a slab plate of an insulating material such as a plaster of paris, which has a spiral wire of alloy nichrome. When the two ends of the wire are connected to the power supply mains, it starts to glow red due to excessive resistance and gives excessive heat.

Electric press

In the electrical press, the wire of nichrome is wrapped on a plate of asbestos. This plate is placed inside an iron or steel casing. Above the cover is attached to hold the handle of any malicious substance. When current flows in the wire, it starts heating and heating. It is used to press clothes in homes.

electric light bulb

The first light bulb was invented by Edison. It consists of a thin coil of oxygen metal. To prevent oxygen of this metal, it is vacuumed inside the bulb. Its cover is made of thin glass. Sometimes instead of vacuuming completely inside the bulb, nitrogen and argon gas are filled in it.

Tungsten metal is used because its melting point is high. Inert gases fill the bulb because tungsten metal evaporates at high temperature in a vacuum and it evaporates and sticks to the bulb walls, this is called blackening. After this process, the fiber weakens and breaks. Typically domestic bulbs are lit at 220 volts.

Tube light

Some substances are such that when high-frequency light, such as ultraviolet light, is applied to them, they absorb it and emit light at low frequency. Such substances are called phosphor and this phenomenon is called fluorescence. Tubelight consists of a long glass tube, with a paste of phosphor on the inside walls. Inert gases inside the tube, such as argon, are filled with mercury. There are two fibers mounted on both sides of the tube like barium oxide. When electric current is passed through the fibers, electrons are emitted into them, ionizing the gas in the tube. The current flows in the tube as a result of the flow of ions produced by ionization. The current in the tube evaporates by obtaining heat and due to this electric immersion produces ultraviolet rays. When these rays fall on the putative phosphor on the walls of the tube, it absorbs them and emits light of lower frequency. The phosphor of the tube is made such that the light produced from it resembles that of sunlight.

Alternating current

A stream, whose magnitude and direction changes with time and after a certain time with its same magnitude in the same direction, is called the alternating current.

I = I0 sin Wt

I0 is the peak value of the current, it is called amplitude of alternating current.

Turnover time

The alternating current arises from a coil moving in the magnetic field. In one round of the coil, the current first goes from zero to maximum in one direction, maximum to zero, and then from zero to maximum and maximum to zero in the opposite direction. This alternating current is called a cycle. The time it takes to complete a cycle is called the period of alternating current.

The frequency

The number of cycles the alternating current completes in 1 second is called the frequency of the alternating current.

The unit of frequency is cycle / second or hertz. The frequency of alternating current used in homes is 50 cycles / second or 50 Hz.

That is, this section changes its direction 100 times in 1 second. In practice, the square root value of the alternating current is expressed as 220v.

The alternating current of the same voltage is more dangerous than direct current. The reason is that the actual value of A.C of 220v ranges from -311v to + 311v, whereas the actual value of D.C of 220v is 220v only.

Weightless stream

When the alternating current flows in the circuit without incurring the power, such a current is called a waterless current. Such a current will flow only if the value of ohmic resistance in the circuit is zero.

Choke horoscope

A choke horoscope is such a horoscope, which allows D.C to be released from inside itself, but causes a blockage in the flow of A.C. The choke coil is made by wrapping a separate copper wire on a core of soft iron. The value of inductance increases due to iron.

The advantage of a choke coil is that due to this, the value of electric energy expended in the circuit is minimum. Choke horoscopes are used in florescent tubes and radios in homes.

Transformer

It is a device that works on the principle of electromagnetic induction, which is a high AC The following AC voltage In voltage and low AC High AC voltage Converts to voltage. The transformer is made by wrapping two coils face to face on a rectangular core of soft cast iron. A.C. The coil connecting to the source is called the primary coil and the outer coil connecting the outer circuit is called the second coil.

Dynamo or AC Generator

It is the device that converts mechanical energy into electrical energy. Dynamo works on the principle of electromagnetic induction. In this, a coil of wires is rotated in a magnetic field by a water turbine or steam turbine. Hence, with the help of dynamos and brushes, the electric currents are sent to the external circuit.

electric motor

It is a device that converts electrical energy into mechanical energy. When a force is acting on the magnetic coil located in the magnetic field, it starts moving through the magnetic field. Thus the electrical energy in the armature is converted into mechanical energy. (Electric motor does not operate on the principle of electromagnetic-induction)

Microphone

Sound energy is converted into electrical energy through this device. This allows the sound to be sent from one place to another. The electrical energy transmitted by the microphone is again converted to sound energy with the help of a second-place loudspeaker or telephone receiver.

Loudspeaker

With the help of loudspeakers, the electrical waves transmitted by the microphone are again converted into sound waves.

Domestic power supply

The power supplied to the homes is an AC of 220v, whose polarity changes after 100 seconds per second, ie its frequency is 50 Hz. The polarity of the current changes twice in a cycle. This is called the main line and the wires through which this current flows are called mains.

Mains are often supplied on two different amperes, which are 5A and 15A. The first is called domestic and the second is called power line.

The reason for the need for two types of supplies is that different types of appliances like bulbs, tubes, heaters, radios, televisions, refrigerators, etc. are used in the houses. Some of these require 5A and some require a 15A current.

Various resistance devices are used in homes. The resistance of the heater is about 20–40 ohms, while the resistance of the bulb is about 20 times higher than that.

If both these devices are connected in series then the current flowing will decrease and each device will not get the appropriate power to work.

Parallel combination reduces equivalent resistance, which increases the current flowing. In this situation each device receives the required energy.

A heater with a resistance of 2 kW and 24.2 ohm draws 9.1 ampere current at 220 volts, but a 100 watt bulb with a resistance of about 480 ohms takes only 0.45 ampere current. Since the power of the two devices is different, their requirements also vary.

Therefore, it is convenient to provide two mains – one for more amperes, which can be used in high power appliances like heaters, coolers, iris, refrigerators, and 5 amperes which can be used for light bulbs and other low power Can be used for equipment.

Domestic wiring

The main supply of electricity in the houses is done by 2 core wires, which are known as electrical, neutral and ground wires. The current wire is usually red in color and current flows through the mains.

The neutral wire is usually black in color and carries back current. The ground wire is usually green in color. These wires supply power to various circuits inside the house.

Electric fuse wire

Such wires are placed in an electric circuit so that currents up to a certain amount of them can flow without loss. If a current of greater magnitude flows in the circuit, the wire will become very hot and may also catch fire. The magnitude of current flowing in the circuit may exceed the permissible limit due to the following reasons –

Overload and
Short circuit
The magnitude of the current in the circuit depends on the power of the equipment to be put into it. The choice of special quality wires depends on the magnitude of the current flowing through them. If the total power of the equipment exceeds this allowed limit, the equipment starts pulling more current than required, this is called overloading.

Sometimes existing and neutral wires come in contact due to bad wires. When this happens, the resistance of the circuit becomes almost zero and excessive current flows through it. This is called shorthand. As a result, the wires become overheated and may cause equipment damage. In places where shortening has taken place, sparks may also arise which can also cause fire.

The most important device for the protection of electrical circuits is the fuse. A fuse is a piece of wire whose melting point of the material is very low. When too much current flows in the circuit due to overloading or shortening, the fuse coil is heated and melted. As a result, the circuit breaks and the current stops flowing in it. The fuse is always attached to the current wire.

Electric shock

When a shock occurs in the body due to electricity, the sensory organ sends that signal to the brain with the help of a neuron in the form of electrical pulses. Its speed is about 120 m / s.

Magnetism in medicine
Electric current always generates a magnetic field. Even the weak ion currents that go along the nerve cells of our body produce magnetic fields. When we touch an object, our nerves carry an electric impulse to the muscle that we have to use. This impulse produces a temporary magnetic field. These fields are very weak and the Earth’s magnetic field is important to generate. They are the heart and brain. The magnetic field within the body forms the basis for obtaining reflections of various parts of the body. One such technique is by the use of a magnetic resonance resonance. Analysis of these reflexes is helpful in medical diagnosis. Thus magnetism has important uses in medical science.

Electromagnetic radiation

Electromagnetic Waves Electromagnetic waves are coupled recurrent electric and magnetic disturbances that are caused by oscillating electric charge.

Electromagnetic waves have a very long frequency range, ranging from a low frequency of 105 Hz radio waves to a frequency even higher than 1020 Hz gamma-rays. Visible light is electromagnetic radiation, whose frequencies range

4.3 × 1014 to 7 x 1014 Hz. It is clear from this that there are no clear boundaries of its diverse blocks, in fact they are overlapped. The descriptive names of various blocks of the spectrum are only historical classification, otherwise the nature from radio to gamma is the same. The only difference in frequency and wavelength is the same nature. The speed of these waves is the same in vacuum. For all electromagnetic waves, the associated equation formula

Speed ​​= frequency × wavelength

If the frequency of a wave transmitted from a radio station is known, then its wavelength can be determined by dividing the given frequency. For example, the wavelength of a radio wave sent from a radio station at frequency 819 is 366mm.

Dispatch of radio and television

When transmitting radio-waves from a radio station, they are received on any area of ​​the Earth by reflecting from the ionosphere (an area of ​​60 to 500m spread across the atmosphere around the earth) in the atmosphere. Some absorption of these waves by the ionosphere slows down the radio signals received over distant areas. Radio reception at night becomes somewhat better because the layers of the ionosphere are not affected by sun rays.

Television signals are transmitted by high-frequency waves, and these waves penetrate the ionosphere, so are not received as radio signals. Television remittances are judged on the basis of line of sight. Thus television programs are available only for a limited distance. Due to the curvature of the Earth, television reception is limited to a limited distance. But now with the help of the developed technology, it has become possible to connect television to any area of ​​the Earth by geostationary satellites.

Galvanometer
A galvanometer is a device that detects the presence of an electric current in a circuit. If the current flowing through it is zero then its indicator remains at zero. It can be deflected to either the left or right side of its zero sign, this deflection depends on the direction of the electric current.

Radar

There are radio waves of very high frequency, which are used for reconnaissance of ships and aircraft. A rotating aerial sends high-frequency radio waves, which return after being reflected from these objects. The distance of the object can be determined by the time interval between the transmit and eclipse of the pulses.

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