**Resistance and Conductance**

**Resistance and Conductance in an Electric circuit**

Here you can find the **complete detail of the theory of electrical resistance and conductance** is useful for competitive exams and **science** students. We hope you would clear all your concept of **electric resistance and** **conductance** from the published post –**Complete detail of electrical circuit resistance and conductance.** The topic **‘Complete detail of electrical resistance and conductance** is written by an expert. The **electrical resistance** is such a physical quantity that is always unwanted quantity in an **electrical** circuit but on the other hand, we utilize its great applications in our life.

The **electric resistance** of any substance is the physical property of a substance that **opposes** the flow of **electric current**, It was a **German scientist Siemon George Ohm** first observe this phenomenon of the matter and discovered **Ohm’s law** in 8 January 1926. He found the relationship between voltage and **current.** **Conductance** is also the physical property of matter which is the ease of flowing **electric current** means it is the ability of a matter to flow a charge in it.

**Ohm’s ‘law** states that **electric current** is directly proportional to the potential difference between the ends of a **conductor**, the **electric resistance** is the physical property of the matter which opposes the flow of **electric** **current.** The unit of **resistance** is represented by the l**ast letter (24 th) of Greek alphabet Ω ** **uppercase** **omega** named **Ohm** after the name of **German Physicist George Simon Ohm.**

Where V is the voltage across a** conductor** and i is the **electric current** generated by the voltage across its ends. The **electric resistance** of **conductors** like silver, copper, aluminum, and iron is low, three of them, copper, aluminum, and iron are mostly used to build **electric** wire because silver is not found abundantly in the earth thereby costlier compared to rest of all the metals. All the matters which allow the flow of the **electric current** is known as the **conductors**. The **resistance** of the matter like plastic, air, soil etc is too higher to allow the flow of **electric current** so these matters are known as insulators.

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The **electric resistance** in a circuit is required to control the **electric current**, the** resistance** of cables and wire is neglected when a net **resistance** of a circuit is calculated. The components that are used to control **electric** **current** are known as **resistors**,you would have seen the filament of an **electric** bulb made of spiral tungsten wire, tungsten is used in that because its **resistance** is higher, this higher **resistance** causes it to heat up enough to glow. The heating elements in the **iron, toaster, electric pan, electric pressure cooker, electric shower,** **etc** are bigger versions of the filaments. Have you observed how a voltage is controlled in a stabilizer or volume of a musical instrument or television, actually in all these cases we increase or decrease the electric resistance through a variable resistor attached with the volume knob.

The **resistance** of a **conductor** is directly proportional to the length of the **conductors,** you can get it through the example of a water pipe, the speed of water is slower in a pipe have more length compared to the pipe of the same radius but of shorter length.The flow of electrons in the wire and the flow of water in the water pipe can be supposed as the same idea.

……..(i)

The **resistance** of the **conductor** is inversely proportional to the cross-sectional area of the **conductor**. You can get it through the example of water flows slower in the thinner pipe compared to the wider pipe if both pipes are of the same length.

……..(ii)

From (i) and (ii) we have

**R= Resistance**

l= length of the **conductor**

ρ = Specific **resistance** of the matter

It is that’s why the **heater wire** and** tungsten wire** is designed into the spiral shape of the coil so as to accommodate its sufficient length in the smaller area of the **heater** and **bulb.**

The combination of the **resistance**– The ways of connecting **resistors** are of two kinds.(i) Series connections (ii) Parallel connections

(i) Series connections- In the **electric** circuit when the positive terminal of one **resistor** is connected to the negative terminal of another **resistor** then such a combination of resistors is known as the series connections.

The net **resistance** of the circuit is the sum of magnitudes of all the **resistors** in series. In series connection, the voltage of the battery is distributed across each resistor in the proportion of their value ,as we know the length is directly proportional to the resistance, so to get the net resistance of the circuit all the individual resistances should be added.

Where is the total net resistance of the circuit

The Parallel Connection – When the positive terminal of all the** resistors** are connected to the positive terminal and the negative terminal of all the **resistors** are connected to the negative terminal of a battery, then such a combination of the circuit is known as a parallel connection. In parallel connection of **resistors,** the voltage across each** resistor** is the same but **current** drawn by each **resistor** is in proportion to their magnitude of the **resistance.**

As we know the resistance is inversely proportional to the area of cross-section of the conductor, hence the net resistance of parallel combinations of resistors is calculated as a sum of reciprocal of their resistance.

Conductance of the Circuit- The conductance(G)of the circuit is inverse of the resistance

From Ohm’s law V = iR

The **conductance** of a substance is the ratio between the **electric curren**t and voltage, **conductance** is the ease with which an **electric current** passes through a substance, when voltage is constant across an **electric** component then **conductance** is directly proportional to the **electric current** flowing through it. Unit of **conductance** is the inverse of **Ohm** i.e **Mho** or **Siemen**, if i =1A and voltage is 1 volt then one unit of conductance is 1 ampere/volt or **1 Mho** or **1 Siemen** or simply **1S.**

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**Conductivity-** As the **conductance** is inverse of **resistance**, on the same way the** conductivity** is inverse of **resistivity.**

The **conductance** of a given material depends on the following physical parameters

The **conductance** of a substance is inversely proportional to the length of the **conductor** and directly proportional to the area of the cross-section of the conductor, therefore it can be expressed in terms of the following formula

The unit of the conductivity is

**Unit of conductivity is Siemen/meter**

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