Electrical conductor

Electrical conductor
electrical conductor

In electrical engineering electrical conductor or a conductor is that type of material that current can flow through it. As metals have low resistance and high conductance they are most used as electrical conductors.

Why are electric Conductors important?

Electric conductors are important because they can pass an electric current through themselves. Electric Conductors can conduct electric energy by themselves. Electric conductors are made of atoms. Atoms have electrons in their valence shell.

The valence shell is referred to as the last shell of the atoms. The electric conductors are normally metals. Metals have a relatively greater size of atoms than non-metals. The bigger size of an atom has a weaker hold on the valence electrons.

When an adequate amount of ionization energy (the energy that can remove an atom from the valence shell/orbit) is provided, the valence electron leaves the atom and starts flowing in the metal. Now, if we observe, only one electron does not leave its atom but millions of electrons leave their atom and thus create a pool of electrons in the metal. When the electrons get energy, they pass it to the next adjacent electron and this process keeps on happening until the energy is passed from one end to the other end.

Conductors are one of the greatest discoveries of science. After the thermal conductors were found, man came to know that energy isn’t only a static resource. It can be used by transferring one part to the other. Thermal conductors can transfer only heat through themselves.

But the Electrical conductors are able to pass heat and Electric current through themselves. Conductors are normally metals. Themetals, due their free electrons, possess the tendency to pass an electric current through themselves. Copper is a commonly used electric conductor.

Wires are conductors of electricity. If you take off the insulation of a wire a shiny kind of material can be observed. This material is mostly Copper. Copper is believed to be the best conductor for household and office wiring. But for some other purposes, other materials are also used.  Such as for the Overhead transmission lines, the wires/cables are made of Aluminum due to their characteristics.

Conductors can be good or bad. Good Conductors provide low resistance to electric current when passed through it. They do not lose break over a long period of time. It means they have a long life. Bad conductors do not let the current pass through themselves easily.

They have high resistance and low conductivity. There is another category that is called super-conductors. Super-conductors can pass electricity from them very easily. They have zero resistance and maximum conductivity.

Uses of Electrical Conductors

The main use of Electrical Conductors is to manufacture electrical devices, machines and equipment. Wires are made of electrical conductors such as copper, and they are a basic example of an electrical conductor usage.

Wires are used to transfer the electric energy from the powerhouse to the houses, offices, and malls. To glow the light bulbs, we need electric conductors such as wires to provide energy to the bulb.

The internet we are using is existing just because of conductors. The internet is a global service. To make it accessible across the globe, the wires made of electric conductors are laid in the deep sea. The mobile phones and laptop we are using have conductors and their applications in them to work.

The electric signal can be transmitted and received using the conductors. Although most of the equipment and gadgets that we use in daily life are seen to be a product made of plastic, the inner circuit is always made of conductors. Electric conductors are used for the heating and molding of jewelry.

Conductors are used to transfer electricity to run the devices such as fans, air conditioner, lights, motors, water pumps, computers, electric cars, radios, televisions, stoves, irons, batteries, and many other things. Conclusively, we can say that electric conductors are an essential part of human life. Without conductors, the world would be totally different place.

Electrical conductor material

Conductors may be metals, electrolyte, metal alloy, or graphite. All these materials allow current to easily pass through them.

Silver is 6% more than copper conductivity, but its not the best choice for  conductor material due to its cost. Silver conductors is rarely used in special applications such as satellites

Although aluminum is only 61% of the conductivity of copper ,aluminum conductors are the best choice for transmission lines, This is due to aluminum is lighter in weight and less in cost compared to copper.

What are the characteristics that make an electrical conductor?

Electrical conductors should conduct electricity. To be a good electrical conductor, a metal should have a high density of free electrons. The greater number of free electrons there, the more will be conductivity. The metal should have low resistance so that the flow of electrons and holes is easy through the metal.

Metals should not have any energy gap between the conduction band and the valence band of their atoms. When the electrons are present in the conduction band, they can move freely. The free movement of the valence shell (or band) electrons allows conductivity as they become the agents of the energy transferring from one end of the body to the other.

The electrical conductors also follow the same concept of energy transfer from a higher energy end to the lower energy end. When the electric potential is applied to the body, it provides sufficient energy to the electrons to leave their atom and start roaming in the free space between the atoms.

Electrons do not take a straight path for their flow but a random path is followed with a particular velocity. This velocity is called the Drift Velocity. The metal, to be a conductor should allow the electrons inside it to have a drift velocity.

Otherwise, the electrons will not flow, and electrical energy will not be transferred from the lower energy (potential) to a higher energy (potential). Conclusively, these properties should be in metal to be a conductor.

  1. Free movement of the electrons inside the metal.
  2. No external charge should be present inside the conductor, only the internal movement of the electrons should be present on the surface.
  3. Electric field should not be present inside the conductor. The conductor should have its electric field around itself. The value of the electric field force inside the conductor should be 0.

Conductor ampacity

A conductor ampacity is the amount of electrical current it can carry, this ampacity is related to its resistance, the lower the conductor resistance the higher the ampacity of the conductor. The resistance is related to the conductor material and size (cross sectional area)

Current passing through a cable faces electrcal resistance, and then produces heat. The temperature of the conductor and the insulation around it rises depending on the current value. Here comes the cable ampacity.

Cable ampacity or current carrying capacity is the maximum current that the cable can carry continuously at maximum operating temperature.

Where to find table of ampacity for cables?

Each cables manufacturer has products catalog. This catalog contains data and tables of the cable electrical and physical properties. Voltage drop, Derating factors, short circuit, table of ampacity and more electrical data are in these tables.

One of the most important tables that every one who works with cables needs it regularly is the ampacity or current carrying capacity tables. The table contains current values that every cable can carry.

In the table we find cable cross section area, in the firs column then resistance and current that each cable size can carry. There are three current values for each cable size. This is because this current value affected by the laying method. Laying the cable in ground, in free air or in duct these are the three methods in the table.

What determines conductor ampacity?

As mentioned above, Cable laying method is one of some factors which affect current carrying capacity of the cable, Other factors are listed below:

  • Conductor material.
  • Insulation around the cable. i.e XLPE or PVC. XLPE insulated cables can carry more current than PVC insulated ones.
  • Laying method of the cable. i.e in air, underground or in duct.
  • Laying in Trefoil or flat formation.
  • Temperature of the ambient air.
  • Soil thermal resistivity.
  • Burial depth underground.
  • Duct inner diameter for cables in duct.
  • Number of cables in the same laying path.

Here under the most common factors that affect conductor ampacity in more details:

  1. Ambient temperature
  2. Duty Cycle of the current passing through the conductor (wire)
  3. Load Requirements
  4. Effect of adjacent wires’ heat

Ambient temperature

The ambient temperature plays role in deciding the ampacity of the conductor. As it is a measure of heat that is why the temperature around the wire must be taken into consideration.

Say, a wire is placed in a place with an ambient temperature of 45 degrees Celsius. As the current ampacity states that the temperature due to current flow should not add more than 30 degrees to the temperature of the conductor.

So, when the current is flown through the wire, the total temperature of the wire must not be more than 75 degrees Celsius.

Duty Cycle

The duty cycle of the wave (current) also matters. The duty cycle is the time for the ON and OFF times of the wave. When it comes to the current flowing through the cable, it is determined by the level of the current flowing through the cable. The level of current i.e., the duty cycle must be of the value that it must not add 30 degrees Celsius to the temperature of the conductor.

Load requirements

The rating of wires should be chosen in essence so that it can cop up the current that is load needs to keep working. Say, a wire that supports 0.5 Ampere current through itself is installed for the load that needs 3 Ampere current.

The wire will simply blow away due to the temperature rise caused by the high value of current. As the high values/ magnitude of current adds more temperature, it is advised to use such a wire that adds less than 30 degrees Celsius to the temperature of the wire.

Effect of adjacent Wires’ heat

Normally, when the cables are installed in big offices and grand malls, there isn’t a single cable supplying all the energy to all the loads. Multiple cables are installed and these cables are normally installed adjacent to each other to maintain the symmetry of the wiring system.

When these cables are close (adjacent) to each other and all of them are emitting heat individually due to the current passing through each of them. This individual heat emission adds up to the temperature of the ambiance.

So, when wiring is done it must be taken care of that the cables should not heat up too much that they melt the insulation away and cause a short circuit.

Cables data, Android app for electricians

Cables tables are used in designing offices and in work site as well. So its important to have cable rating tables on your hands. This app has cables tables and data, like ampacity , Voltage drop, derating and short circuit tables. The app is 100% free. But it has Ads free paid version, you can switch to it later.

Copper conductor

Copper conductor is being used in many electrical industries and applications, such as electrical motors transformers and generators windings, power cables, small wiring wires and so many applications

Copper conductivity

The measure of how well any material transports electric charges is known as electrical conductivity. Copper has the best and highest electrical conductivity of all metals except precious metals.

Why is copper a good conductor of electricity?

Copper is one of the best conductors of electricity because it is very good metal. It has high metallic properties. It can be molded into whatever is needed. It can be shaped into wires of any radius. It has high ionization energy as compared to other metals.

But the ionization energy of copper is lesser than that of copper and aluminum. It means it is relatively easier to generate free electrons in copper than to generate free electrons in silver and aluminum. So, provided low energy, copper still has free electrons in itself.

These free electrons have high kinetic energy due to which the current can pass through the copper metal. Apart from its electrical properties, copper is preferred to be used as it is readily available. Copper costs lesser than other good metals.

Due to its good conductivity, it is widely used in microelectronic circuits. The circuitry of Televisions, micro-controllers, mobile phones, etc. is mainly made of copper. Micro-processors such as the ones used in new personal computers are also made of copper due to their good conductivity and low resistance.

Motors, compressors, and wiring of houses and offices are done using copper due to its good conductivity and low resistance. Copper offers good electric current flow through itself which makes it better than other metals.

Why is copper not a super-conductor?

Copper is not a super-conductor because it does not follow the properties of super-conductors. Some properties that a conductor like copper must follow to be a super-conductor are:

  • Critical Magnetic field
  • Expulsion of the magnetic field.
  • Infinite Conductivity
  • Transition temperature

Copper does not follow these properties. Like if copper has to be a super-conductor, it must follow the critical magnetic field property that states that beyond a particular value of the magnetic field, copper will lose its conductivity. This does not happen with copper.

For the second property satisfaction, copper should not let any magnetic field penetrate itself. While in the case of copper, magnetic fields can penetrate copper easily. For the property of infinite conductivity, copper must offer 0 resistance to the current that flows through itself.

And after a critical temperature, the conductivity of the metal (copper in this case) should be infinite. That too is not possible in the case of copper. The transition property suggests that the metal becomes a super-conductor at a particular temperature called transition temperature.

This temperature is achieved by increasing the temperature of the metals not decreasing it. But if we increase the temperature of copper, instead of becoming a super-conductor, it melts away. Keeping all these situations in mind, we can say that copper is not a super-conductor.

Copper vs aluminum conductors

Copper and aluminum conductors are the most popular electrical conductors, but copper conductivity is better than aluminum , while Aluminium has only 61% of the copper conductivity. But aluminum is less in weight and cost.

So aluminum conductors are preferred in long distances overhead transmission line. While in electrical motors, generators transformers winding, copper is the best choice.

Copper conductor ease of installation

The mix of hardness, strength, and flexibility of copper make it very easy to work with in electrical installations,  no special tools are needed for copper wiring.

Can a copper lugs be used for aluminum cable?

When connecting cooper to aluminum cables galvanic action takes place, to avoid this galvanic action it is highly advisable to use a special copper aluminum lug, which is well known as Bi-Metal lugs.

Copper conductor and theft

Copper prices increased  allover the world, this increased criminals wish to steal power supply and communications cables copper.

Aluminum conductor

Aluminum conductor is that conductor which is made of aluminum, its widely used as aluminum is considered a good conductive material
Electrical conductor is a type of material that allows electrical current to pass through it.

  •  Aluminum conductor is only about 60% of the conductivity of copper conductors, and is the most common metal in electric power transmission lines.
  • Aluminum has only 30 percent of the weight of copper wires.
  • Are used in electrical circuits, wiring and even in high voltage power transmission lines (HV OHTL)

Aluminum wires mechanical and chemical properties are the main disadvantages of it.

Aluminum Conductor ampacity

The ampacity of any conductor, is the electrical current amount that conductor can carry, ampacity is related to electrical resistance. A conductor with lower-resistance can carry a larger current, and because copper has lower resistance than aluminum, So a copper conductor with the same cross sectional area of an aluminum one can carry larger value of electrical current.

Aluminum in electrical motors

Copper is the most used wires in motor winding, however aluminum is used too but not so much, Using copper is technically more useful and easier. Using aluminum in motor winding with the same number of turns of a copper winding results in lower power of the motor.

Why do electric Conductors get hot?

Due to the vibration of electrons, conductors get heated up. Electricity is a form of energy and conductors are the agents that pass this energy through themselves. The conductors are made of metals. All the metals are solid except mercury.

So, almost all the metals can conduct electricity by themselves. When Electric current is passed to one end of the conductor, the atoms get energized. This energy ionizes the atoms and atoms lose their valence electrons. These electrons get kinetic energy and start moving in the metal.

This motion is not a proper motion. This motion is a vibration of atoms about their mean position. This vibration makes the conductor hot. When atoms vibrate, the flow of current through the metal is a little suppressed. This phenomenon is called resistance.

So, resistance is the main reason for the conductors getting hot. When many conductors (insulated from each other) are placed with each other and there is no proper airflow and ventilation in that place, the conductors get more heated.

Another reason for conductors getting hot is passing higher magnitude current through them. Conductors offer more resistance to higher value of current. Increasing the current increases the resistance.And due to more resistance, there will be more heating up of the conductor.

How to reduce overheating of wires?

Some common methods to reduce overheating of wires are:

1: Use the wire of proper rating. If the wire connected from source to load isn’t chosen according to the rating of load, it will overheat and may damage the load or itself. If a load requires 220 volts of the potential difference. A wire rating 220 volts or higher must be used. The rating of the wire is written on it.

2: Wiring should not be congested. Each wire emits a specific amount of thermal energy due to the phenomenon of resistance. When wiring is congested, the heat is accumulated. This may cause a fatal accident.

3: Ambiance can be a factor in heating up wires. So, it is advised not to wire in direct sunlight.

4: If the wire is uncomfortably hot, then we must change the wire with a wire of proper ratings.

5: Sometimes a short circuit that was unable to blow off the fuse, may become a reason for heating up of wires. In DC circuits, this phenomenon is observed.

6: Corrosion also causes overheating of wires. Corroded wires have more resistance, this resistance sometimes exceeds to a point that it melts off the insulation from the wire. So, corroded wires must be replaced with new ones to avoid overheating.

7: Overloading of wires must be avoided at any cost. Because if a wire is overloaded, it does not pose a threat only to the wiring but to the load too.

8: Poor connection leads to overheating of wires because they lose connection and can offer periodic sparking of current. This sparking leads to overheating of the wires.

10: If there are loops or coils in the wiring, it causes overheating. The reason is as same as the reason is for placing too many wires, at the same place, thatis conducting current through themselves.

What causes wires to melt?

Improper and loose connections as well as short circuit cause the wires to melt.

An Improper connection could be of any type. Like if a connection made in such a way that the total load it is supporting is way greater than what actually it can support, the wire will melt. Let us understand this concept with an example.

Say, Mr. Clint, installed a new AC in his office. This is a brand new 5-star AC that needs a starting current of 20 Amperes. Now he wanted not to add the cost of an electrical engineer who will use his knowledge for the wiring. He bought a wire like the one he used for his ceiling fan and made a connection for his new 5-star AC. The wire melted in a fraction of a second after he switched it on. Now, the reason is that this wire has a current rating of 0.6 Ampere while the suitable rating was a 20 or 20+ amperes rated wire. So, this kind of improper wiring should be avoided.

Another major reason for melting wires is due to combinations. If a part of the circuit is wired perfectly and wires are used according to the ratings. But in the other part of the circuit the choice of wires according to what the ratingsare, that part of the circuit will overheat. And according to the laws of thermodynamics, the heat flows from the hotter part of the body to the colder one. The heat of a loosely bound circuit will spread to the perfectly placed circuit too. That can become a reason for the melting of the whole circuit. So, the circuit should be designed carefully.

Multiple extensions of a wire also cause the melting of the wires. It is not something that is not realized directly. But if we observe the extensions of the same wire are actually increasing the load on a wire step by step. If the total load that is being supplied with electrical energy using the wire becomes greater than the rated value of the wire. The wire will melt.

Why does the human body conduct electricity?

Would not it be surprising, if I tell you that a human body has the electricity of its own? Yes! The human body has its own. The nervous system needs impulses to conduct messages. These impulses are made of electricity. So, if the human body can have electricity of its own, then it can also conduct electricity itself.

Now the process of electrical conduction is possible due to the composition of the cells that are present in the human body. The cell is the basic structure of the human body that has many sub-cell particles. Such as the nucleus, mitochondria, cytoplasm, etc. These sub-cell particles are made of atoms such as chlorine, potassium, and sodium.

These atoms are not in stable form but they react and form their ions. The ions of sodium, potassium, and chlorine. These particles are able to conduct electricity through them. As the neurons are responsible for the conduction of human current, the external current is also transmitted through them.

When an external current enters the body, it enters due to the moisture present on the body surface. Then a neuron intercepts the current and as it is a conductor, it (neuron) allows the current to pass through itself. The voltage of human current is as much as we can not feel.

But the external current always possesses a higher voltage than the voltage of human power. So, dendrites transmit this higher power and it hurts when it passes through the body. if our body is not in contact with any other medium than the current source itself, we will not feel the current.

For example, if an electrician is working in the house and he is wearing plastic (or any other insulator) boots and he touches wire with just one hand while the other hand is not in contact with anything, he will not feel the current. the reason is that the current needs a ground (neutral for a layman) to complete the circuit.

The electrician isn’t electrocuted because he has the same potential as the wire and there is no other potential known to his body right now. (IT IS STRONGLY ADVISED NOT TO TRY THIS YOURSELF AT HOME).

Is water a conductor or insulator?

Pure water is an insulator. As pure water is a molecule of Hydrogen combined with an atom of oxygen using hydrogen bonding, there is no free ion or even a free electron in pure water. The structure of water does not allow the current to flow through itself.

Current needs free electrons to pass energy.Water that is H2O does not have any free electrons. It has a very powerful covalent bonding called Hydrogen bonding that does not let it break into atoms or ions easily. Although, pure water is available in laboratories only.

It is prepared by scientists. The water that we drink and use occurs naturally and isn’t only H2O.It has various compounds of calcium, potassium, and other minerals based on where it is present. Water near the mountains of chalk will have a high concentration of calcium ions.

These calcium ions can transmit energy through them and also allow the electric current to pass through themselves. Thus, this water is not an insulator. It becomes a weak conductor that can pass a very small amount of electric current through itself.

Water present near the salt mines has the ions of sodium and chlorine present in them, these salts also have the tendency to pass the current through themselves.

Conclusively, we can state that water in its pure form does not conduct electricity but naturally occurring water conducts the current that can be felt when someone comes in contact with it.

Can distill water conduct electricity?

NO! Distilled water is an insulator. Distilled water can not conduct electricity through itself. Distilled water is purified water that does not have any minerals or ions in it.

As we know H2O is an insulator in its pure form, it cannot conduct electricity. The same case is with the distilled water. It is also H2O. The difference in both of these is that pure water is produced in the laboratory while the distill water is a purified form of naturally occurring water.

When naturally occurring, water is passed through the process of removal of ions and minerals, the conductive elements of water are actually removed. These minerals and ions were actually the conductive agents in the water. When they are removed, water becomes an insulator.

Engineers have proved this phenomenon of insulator water in many ways. One way to check it is to take a bowl and fill it with the distill water. Then put the live wire of 120 Volts AC current in the water. Now take a 20 W blub and join the neutral terminal of the bulb with the neutral of AC supply.

Then put the live wire in the water bowl. The bulb will not glow as the resistance of distilled water is much greater than to let the current pass through the water. (IT IS STRONGLY ADVISED NOT TO TRY THIS YOURSELF AT HOME).

How to increase the conductivity of water?

There are several methods of increasing the conductivity of the water. Some of them are discussed below.

Increasing the temperature:

The increase in temperature makes the inter-molecular forces of water weaker. Weaker forces let the electron leave the valence shells and thus these electrons play part in the transferring of the electrical energy.

Adding Ions:

By adding the ions or a compound that ionizes in the water, we can increase the conductivity of water. For a simple example, we may consider adding non-iodized table salt to the water. When pure salt NaCl is added to water, it ionizes into Na+ and Clions. These ions have a high tendency to conduct electricity. So, when these ions are present in the water and the current is tried to pass through the water, the current passes easily.

Adding Acid:

Adding a small amount of acid to the water also increases the conductivity of water. Water ionizes the acid and this process is called Electrolysis. Through the process, water transforms into an electrolyte. Electrolytes are highly conductive.

Is stainless steel a good conductor of electricity?

Stainless steel is an electrical conductor. But it is not a very efficient electric conductor. The resistivity of stainless steel is about 40 times more than that of copper. If you want to make electrical components using stainless steel then you’re not investing you’re wasting your money.

Although, stainless steel is an alloy of two metals i.e., steel and nickel. But the stainless steel does not conduct as good as well as steel does. One of the good things about stainless steel is that it can be molded into shapes. Say if someone wants to make antennas using stainless then it is highly recommended.

Most of the car antennas we see on the roof of the cars are stainless steel plated. It does not rust easily. It has a very good shining appeal that looks very good to the viewer.

But due to the higher value of its specific resistance i.e., 6.7×10-7 ohm-meter it is not considered a reliable conductor for wiring and other electrical components.

Is glass an electrical conductor or an Insulator?

Glass is an insulator. Glass in its normal state (solid-state), at room temperature is a very good insulator. But when heated to a very high temperature it can conduct electric current through itself.

The reason is in solid-state, room temperature glass has a very good, fixed structure due to strongly bonded compounds. When glass is heated, it melts after a certain temperature and starts conduction. When the glass melts it loses its solid structure and becomes fluid.

This fluid has weaker intermolecular forces and has free electrons in it that allow conduction. Glass does not melt until it is heated from 1300-degrees Celsius to 1600-degrees Celsius. The resistivity of glass is 108 times the resistivity of copper. This makes it impossible to conduct the current using copper in normal conditions.

Is plastic an electric conductor or an Insulator?

Plastic is an insulator. The structure of plastic consists of strongly bonded atoms. These atoms have strong intermolecular forces that are not easy to be broken. A very high amount of energy is required to break these intermolecular forces.

Yet there are some plastics that can conduct electricity. The polar polymers have a tendency to conduct current through them. As the polar polymers have positive and negative poles, and an electric is passed through the polar polymer, it conducts.

The reason is “Dipole Moment”. The dipole moment makes it possible to shift electrons (and so the holes) from one point to the other. A good example of conducting plastics is Polyanilines.

Do electrical conductors conduct heat?

Yes. Electrical conductors conduct heat very effectively. Almost, all of the electrical conductors are metal. Metals are the best Thermal conductors. (Materials that can conduct heat are called thermal conductors).

The basic condition for the conductors to be conductive is to transfer the heat/ electricity from one end of their body to the other end. In doing so, they use their free electrons. When heat is applied at one end of the electrical conductors, the free electrons get energized and pass the energy to their adjacent electrons.

As the metals have free electrons throughout their body, every electron does have an adjacent free electron. Say, we have a copper pipe. Copper is a good electrical conductor.

Assume that we have the facility to see the atoms from atom number 0 to 99. We put a heat source at the end and it will generate an electron where atom 0 is located. Now 0 will pass the energy to 1, 1 will pass it to 2, and so on until 98 passes the energy to 99. In this way, electrons are passed that pass the energy to the other atoms.

These atoms have a physical distance between each other and energy is passed when these atoms vibrate and pass the electron to the next atom. So, due to this distance, energy travels from one end to the other. Even very bad conductors of electricity are sometimes good conductors of heat.

A very common example of this is the Air. Air is a very bad conductor of electricity. Air conducts at very high temperatures when the gases in the air ionize and emit some of their loosely bound electrons.

These electrons then can conduct electricity. But in the case of thermal conductivity, not a very high temperature is required. We see in our daily life if we are sitting in an air-conditioned room and warm/ hot air is present outside the room, whenever someone enters or exits, the temperature of the room increases.

This is because the air has a higher temperature and when it enters the room, it loses its high energy of the atoms present in itself to lower energy atoms of air that was present in the room.

Why is humid air a better electrical conductor?

Humid air is a better electrical conductor because it has moisture in it. When it is raining or snow is falling, the air gets moist. The presence of water vapors in the air increase and air become conductive. Now we have to realize that this conductivity is effective for the static charge. It means that if a body that has a static charge present on it and is placed in the humid air, it is more likely for the body to lose its static charge now. Static charge is developed on a body due to the process of induction. When a body is rubbed over another body both bodies get charged oppositely. Now if we place these bodies outside and check if they are charged or not. We will find out that there will be no charge on them because the humid air takes the charge from the body and spreads the charge on itself. The humid air conducts the static charge.