Electrical Circuit elements:

Concept of ENERGY FLOW, with the help of this energy flow we will try to understand the property and behavior of electrical circuit elements.

Fig.1 Energy flow in power system

When energy flows from source to load, not 100% energy transferred to the load some energy get lost during this process in the form of heat, many things happen to the energy like transformed, unavailable and Stored.

1) Circuit Element Transformed: Energy transformed from electrical to mechanical, electrical to magnetic and electrical to heat energy.

2) Circuit Element Unavailable: Some energy will get lost, it means during the process of energy flow it will become unavailable to the load, some amount of energy will dissipate as heat.

3) Circuit Element Stored: During energy flow energy can be stored in two forms either in kinetic form or potential form, later can be recovered and send either to load or back to the source.So, the energy lost in the component is resistor(R), energy get stored in the kinetic form, component call as an Inductor (L) and in capacitor(C) energy is stored in the form of potential energy.

As we all aware any electrical circuit mainly consists of these elements viz resistor, Inductor and capacitor. Property of these elements are resistance, inductance and capacitance respectively.

We will see all the elements one by one to know them in more detail in below chapters.

RESISTOR

DEFINITION OF RESISTOR: Resistor is not a dynamic component, it doesn't have history, memory and the past state.

It is the algebraic component, whatever is given to the input same will come as output.

✓ Property of Resistor:

• Dissipative

• Lossy

Characteristics of Resistor: Generally, we characterize the component in IV curve.

Fig.1 Characteristics of Resistor

Fig.2 Characteristics of Resistor

When resistor line aligned with the current(I) axis then slop will be zero and R will be infinite, which means it will represent short circuit at y axis. When resistor line aligned with the voltage(V) axis then slop will be zero and R will be infinite, which means it will represent open circuit at x axis. For this refer fig.1.

With the reference of fig.2

current (I)= Voltage (V)/Resistance (R) --------(1)

Or V=IR -------- Equation(2)

This is known as ohm's law.

POWER DISSIPATION IN RESISTOR:

P=VI

Where,

V is the voltage across the resistance.

I is the current through the resistance.

According to equation (2)

P=(V*I)*I

P=I²R

According to equation (1)

P=V*(V/R)

P=V²/R

Resistance:

A material has property to oppose the flow of electrons through a given material, it is known as resistance of material. Different material has different resistivity like Aluminium, copper and gold has value of 2.82*10^-8 ohm-m, 1.72*10^-8 ohm-m and 2.44*10^-8 ohm-m respectively.

Thus, resistance restricts the flow of electrons in the circuit.

What is the flow of electrons?

Flow of electrons is current, and current is nothing but the flow of electrons in the material/conduct.

As per the ohms law:

R=V/I

Where

R is resistance of the circuit,which is considered as 1 ohm.

V is voltage of the circuit, which is considered as 1 volt.

I is current of the circuit, which is considered as 1 Ampere.

Note: When electric current flow through the conductor it will generate heat due to collision of electrons within atom.

HOW TO FIND THE VALUE OF RESISTOR?

Fig.3 Resistance Value

Fig.4 Resistance Value

Now we will see how to find the resistor value?

Consider the above figure of resistor

Y B R

4 6 2

This is the resistor value = 46*10² ohms

Third value is the multiplier.

Note: keep in mind the last colour code of the resistor shows the tolerance, which means variation of resistance with temperature.

RESISTOR SYMBOLS:

RESISTOR SYMBOL:

Fig. 5 Symbol of resistor

There are mainly two type of resistor available:

Fig (a): Fixed resistor.

Fig (b): Variable resistor.

Difference between fixed and variable resistor:

✓ Fixed resistor: This type of resistor value can't be varied once installed in the system.

✓ Variable resistor: Resistor value can be adjusted at any time and any instant.

What is the Rheostat?

This is very useful to control the current of any circuit by varying the resistance.

To know more about resistor please visit the given link:

Elements of electrical circuit- Resistor

INDUCTANCE:

Fig.6 Inductor

Property of Inductor:

A material has property to oppose any change of magnitude or direction of current passing through the conductor, this property known as inductance. Its unit is Henry(H).

In other word we can say that, whenever current passes through a conductor, inductance will oppose any change of magnitude and direction.

Inductance will be one Henry, when current through a coil of conductor changes at the rate of one ampere/second generating one volt across the coil.

Take one meter of conductor, twist it, it will become a simplest Inductor / coil.

As per the ampere’s law when current will flow through a conductor, an electromagnetic field will be formed around the conductor. However, if flow or direction of current will change, the EMF changes.

Due to this phenomenon voltage (V) will generate across the coil,

v =L di/dt

Where,

i is the current passing through an Inductor in Amp.

v is the voltage across an Inductor or coil.

Voltage across coil/Inductor will be zero if current through an Inductor remains constant, there will not be inductance during steady state condition. It will make coil/Inductor to behave as short circuit while switching across the d.c. voltage and act as open circuit during steady state condition.

If current magnitude or direction will change then inductance will appear in the coil or Inductor.

Equation for power absorbed by Inductor:

P =Vi= Ldi/dt . i

= Lidi/di watts

Energy storage equation:

E=1/2 Li Joules

To know more about other Elements of electrical circuit please visit to below links.

CAPACITANCE

Definition of Capacitance:

Definition of capacitance is, it’s a property of element to store/absorb electrical energy within it. Capacitor is an energy storing element. A capacitor stores electric energy in the form of potential energy in between two polarities of charges (i.e. positive and negative charges) on the two electrodes of a capacitor. Measuring unit of capacitance is farad.

Fig.7 Capacitor

Difference between capacitor and resistor is, capacitor can store the energy whereas resistor cannot store the energy.

Element in the circuit which has capacitance, namely known as capacitor.

Q stands for amount of charge can be stored in a capacitor in the form of capacitance.

V stand for voltage against which the capacitance.

C = Q/V

or C = q/v

Q = CV

Where,

CV is equal to i*t [ Steady state equation Q = i * q]

i stand for charging current of capacitor.

t stand for time required to charge the capacitor.

Equation for capacitor to absorb/store power/energy is given by:

Power absorption equation:

P = VI

= CV dV/dt [ i = v dv/dt under dynamic condition ]

Energy storage equation:

E = 1/2 CV² Joules

Note: Capacitor has property to block dc power and allow ac to pass.

Why capacitor blocks dc we will discuss in next session.

To know more about other Elements of electrical circuit please visit to below links.

Electrical Circuit elements:

1) Circuit Element Transformed: Energy transformed from electrical to mechanical, electrical to magnetic and electrical to heat energy.

2) Circuit Element Unavailable: Some energy will get lost, it means during the process of energy flow it will become unavailable to the load, some amount of energy will dissipate as heat.

RESISTOR