Circuit Elements:
Basic Elements of Circuit and Networks are Resistance, Inductance and Capacitance.
Resistance:
The Passage of electrons through a material is not accomplished without collisions of the electrons with other atomic particles.
These collisions are not elastic and energy is lost in each collision.
"The amount of energy lost by the electrons is related to the physical properties of a particular substance. This physical property of a material by virtue of which it opposes the flow of electrons through the material is known as Resistance."
Resistance is denoted by 'R' or 'r' and unit is Ohm.
R= pl/a
p = resistivity of material (reciprocal of conductivity)
l = Length of material
a = Area of cross-section of material
* Extension of wire result into increase in length and decrease in area of cross-section therefore resistance of wire increases.
* For Compression resistance decreases.
* Resistance converts electrical energy in to heat energy.
* When circuit resistance is approaching to zero(0) then circuit is called as short-circuit.
Ohm's Law:
A German physicist George Simon Ohm, investigated the relation between current and voltage in a resistor.
"At constant temperature, the potential difference across the terminals of a resistor R is directly proportional to the current i flowing through it.
i.e. if current supply will increase in a circuit then at resistor voltage drop will be increase.
V=iR
Ohm's law can also be expressed in terms of conductance G, which is reciprocal of R
i= Gv
Types of Resistor:
- Liner Resistor
- Non-linear Resistor
When resistive element obeys ohm's law then the element is called linear resistor otherwise it is called Non-linear resistor.
Power Dissipation in a Resistor:
P= vi = (iR) i = v square /R = v square G
Temperature Effects on Resistor:
The Medium temperature is the temperature of the gas, liquid or solid surrounding a resistor. when the medium temperature is varied then a change in resistance is noted. increase in temperature causes molecular movement within the material. the drift of free electrons through the material is obstructed. this fact causes the electrical resistance of the material to rise and it is called the positive temperature coefficient.
On the other hand, a temperature increase in certain materials, particularly in semiconductors, leads to decrease in resistance and is called as the Negative temperature coefficient.
To read Previous Theory on Circuit elements kindly visit the following link given below:
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