ELECTRONICS

ELECTRONICS

Electronics is the branch of physics which deals with development of electron emitting devices, there use and control of electron flow in electrical circuits. Electronics also deals with semiconductors, diode, rectifiers etc.

RECTIFIER

A rectifier is a device which is used to convert alternating current (AC) into direct current (DC).

PN-junction diode is used as a rectifier.

RECTIFICATION

The process of converting alternating current into direct current is called rectification.

DOPING

Addition of an element of group 3rd-A or 5th-A to Ge or Si crystals to convert them into semiconductor substance (p-type or n-type) is called Doping. Normally impurity is in very small quantity. There are two types of impurities that are added to geranium or silicon:

• Donor impurity
• Acceptor impurity

PN - JUNCTION DIODE OR SEMICONDUCTOR DIODE

INTRODUCTION  

A pn - junction diode is an electronic device formed from a p-type and an n-type substance semiconductor. A semiconductor diode has the property of one way conduction i.e. it allows electric current to flow in only one direction.

WORKING OF pn-JUNCTION DIODE

As we know that a p-type substance has excess of mobile positive charge or holes and n-type substance has an excess of negative charge or electrons, the electrons from n-type and holes from p-type sections flow across the junction and combine. In this way a layer of positive charges is formed on the n-type and a layer of negative charges on p-type material.

Due to induction of these layers a potential barrier is now developed across the junction and further flow of charges is prevented from one side to the other.

TRANSISTORS

A three terminal semiconductor electronic device is called transistor. Transistors are widely used in electronic appliances such as computers, radio, audio video equipment, bio medical instrument etc.

TYPES OF TRANSISTORS

• pnp-Transistors
• npn-Transistors

ESSENTIAL PARTS OF TRANSISTORS

There are three essentials parts of a transistor

Base:

It is the central layer denoted by b.

Emitter:

It is the outer layer denoted by e.

Collector:

It is the outer layer denoted by c.

Therefore only few holes combine with electrons and the remaining holes cross into the collector and generates collector current Ic. In this way almost the entire emitter current flows in the collector circuit. From the above description it is clear that:

Ie = Ib + Ic

Thus there are two current paths through a transistor. One is the base-emitter path or input and the other is the collector-emitter path or output. 

ELECTRICITY

COULOMB

It is SI unit of electric charge. One coulomb (1C) of charge being that quantity of charge which when placed one meter from an identical charge in vacuums repels it with a force of 8.99 x 109 N.

INSULATORS

Insulators are those materials, which do not allow electric charges to pass through them.

In other words, insulators are materials that do not allow electrical current to pass. In insulators electrons are tightly bounded to their atoms. Insulators do not have free electrons.

EXAMPLES:

Plastic, rubber, wood, glass etc.

CONDUCTOR

Conductors are those materials, which allow electric charges to pass through them.

In other words, conductors are materials that allow electric current to pass. In conductors electrons are loosely bounded to atoms. Conductors have free electrons.

EXAMPLES:

Copper, Gold, Aluminum, Silver etc.

VOLT

Unit of electric potential and potential difference in SI system is called Volt.

It is defined as

"In an electric field potential b/w two points is 1 volt if the amount of work done in moving 1 Coulomb charge from one point to another point is 1 Joule."

POTENTIAL DIFFERENCE   

Potential difference b/w two points A and B is equal to the amount of work done by moving a unit positive charge from point A to point B against the electric field

V_B-V_A=V_AB 
or
V_AB= (work)_AB/q

UNIT

Volt or Joule/Coulomb

ELECTRIC CURRENT

The rate of flow of electric charge through a cross section of a conductor is called Electric Current or Electric charge passes through a cross section of a conductor is called Electric Current.

It is denoted by I.

AMPERE

If one coulomb of electric charge passes through a cross section of a conductor in one second, the amount of current passes through it is called Ampere. 1A = 1c/1sec.

CAPACITOR

Capacitor is an electronic device, which is used to store electric charge or electrical energy. A capacitor stores electric charge on its plates. There are a number of types of capacitors available.

CAPACITANCE

Charge storing capability of a capacitor is called capacitance of capacitor.

DEFINITION:

Capacitance of a capacitor is defined as the ratio of the charge stored on any of the plates of capacitor to the potential between the plates.

RESISTANCE

Opposition offered by the atoms of a conductor in the flow of electric current is called Resistance. It is a hurdle in the flow of electric current. Different substances have different resistance. Resistance of a conductor increases with the increase in temperature.

It is denoted by R.

UNIT

Ohm

COMBINATION OF RESISTORS

Resistance can be joined to each other by two ways:

1. Series combination

2. Parallel combination

DISADVANTAGE

If one component is fused, then the other components of circuit will not function.

EQUIVALENT RESISTANCE IN SERIES COMBINATION

Consider three resistances R1, R2, & R3 connected in series combination with a power supply of voltage. Potential difference of each resistor is V1, V2, & V3 respectively. Let electric current I is passing through the circuit.

ADVANTAGE

In parallel combination of resistors, if one component of circuit (resistor) is damaged then rest of the component of the circuit will perform their work without any disturbance. It is due to the presence of more than paths for the flow of electric current.

EQUIVALENT RESISTANCE IN PARALLEL COMBINATION

Consider three resistances R1, R2 & R3 connected in parallel combination with a power supply of voltage V.

JOULE'S LAW

INTRODUCTION:

When an electric current passes through a wire heat energy is produced. It is due to the collision of     electrons with the atoms. In order to continue steady current, work has to be done on electric charges.

STATEMENT:

Amount of work done on electric charge on steady current is directly proportional to amount of heat.

Work a Heat

PROOF:

Consider a conductor through which electric current q is passing in time t let the potential difference between two ends of wire is V.

OHM'S LAW

INTRODUCTION

Ohm’s law is a quantitative relation b/w potential difference and electric current.

STATEMENT

According to Ohm’s law,

"The electric current passes through a conductor is directly proportional to the potential differences between the ends of conductor, If physical conditions of conductor remain constant."

STATICS

STATICS

Statics is the branch of mechanics which deals with the study of bodies at rest under a number of forces, the equilibrium, conditions of equilibrium, types of equilibrium and torque etc.

EQUILIBRIUM

A body is said to be in equilibrium if it is at rest or moving with uniform 

velocity.

In other words if the linear and angular acceleration of a body are zero, the body is said to be in equilibrium.

Or we can say that when two or more forces act on a body such that their resultant or combining effect on the body is Zero and the body retains its state of rest or of uniform motion then the body is said to be in equilibrium.

EXAMPLE

A book lying on the table, suspended bodies, all stationary bodies etc.

CONDITIONS OF EQUILIBRIUM

There are two conditions of equilibrium are as follows

• First condition of equilibrium
• Second condition of equilibrium

STATES OF EQUILIBRIUM

There are three states of equilibrium:

• Stable equilibrium
• Unstable equilibrium
• Neutral equilibrium

STABLE EQUILIBRIUM

When the center of gravity of a body lies below point of suspension or support, the body is said to be in STABLE EQUILIBRIUM.

EXAMPLE

A book lying on a table is in stable equilibrium.

UNSTABLE EQUILIBRIUM

When the center of gravity of a body lies above the point of suspension or support, the body is said to be in unstable equilibrium

EXAMPLE

Pencil standing on its point or a stick in vertically standing position.

NEUTRAL EQUILIBRIUM

When the center of gravity of a body lies at the point of suspension or support, the body is said to be in neutral equilibrium.

EXAMPLE:

Rolling ball.

TORQUE

The torque or moment of force can be define as

“The tendency of a force to produce rotation in a body about an axis is called torque or moment of force."

Positive torque:

If a body rotates about its axis in anti-clockwise direction, then the torque is taken positive.

Negative torque:

If the body rotates in the clockwise direction, then the torque is taken as negative.

CENTER OF GRAVITY

The center of a body is that point in the body through which the resultant forces due to the earth’s attraction possess and through which the whole weight of the body always acts.

OR

Center of gravity of a body is a point where total weight of the body is concentrated.

Introduction To Scalars & Vectors

SCALAR QUANTITIES

“Physical quantities which can completely be specified by a number (magnitude) having an appropriate unit are known as "SCALAR QUANTITIES".

Scalar quantities do not need direction for their description.
Scalar quantities are comparable only when they have the same physical dimensions.
Two or more than two scalar quantities measured in the same system of units are equal if they have the same magnitude and sign.
Scalar quantities are denoted by letters in ordinary type.
Scalar quantities are added, subtracted, multiplied or divided by the simple rules of algebra

EXAMPLES

Work, energy, electric flux, volume, refractive index, time, speed, electric potential, potential difference, viscosity, density, power, mass, distance, temperature, electric charge, electric flux etc.


VECTORS QUANTITIES

“Physical quantities having both magnitude and direction with appropriate unit are known as "VECTOR QUANTITIES”

We can't specify a vector quantity without mention of direction. 
Vector quantities are expressed by using bold letters with arrow sign such as:

Vector quantities cannot be added, subtracted, multiplied or divided by the simple rules of algebra.

Vector quantities added, subtracted, multiplied or divided by the rules of trigonometry and geometry.

                                  

PARALLELOGRAM LAW OF VECTOR ADDITION

According to the parallelogram law of vector addition:

"If two vector quantities are represented by two adjacent sides or a parallelogram then the diagonal of parallelogram will be equal to the resultant of these two vectors."

RESOLUTION OF VECTOR

DEFINITION

The process of splitting a vector into various parts or components is called "RESOLUTION OF VECTOR" These parts of a vector may act in different directions and are called "components of vector".

We can resolve a vector into a number of components. Generally there are three components of vectors.

Component along X-axis called x-component

Component along Y-axis called Y-component

Component along Z-axis called Z-component

Here we will discuss only two components x-component & Y-component which are perpendicular to each other. These components are called rectangular components of vector.

MULTIPLICATION OF A VECTOR BY A SCALAR

When a vector is multiplied by a positive number (for example 2, 3, 5, 60 unit etc.) or a scalar only its magnitude is changed but its direction remains the same as that of the original vector.

If however a vector is multiplied by a negative number (for example -2, -3,  -5, -60 unit etc.) or a scalar not only its magnitude is changed but its direction also reversed.

DIVISION OF A VECTOR  BY A SCALAR

The division of a vector by a scalar number (n) involves the multiplication of the vector by the reciprocal of the number (n) which generates a new vector.

Let n represents a number or scalar and m is its reciprocal then the new vector is given by:

ADDITION OF VECTORS BY HEAD TO TAIL METHOD 

(GRAPHICAL METHOD)

Head to Tail method or graphical method is one of the easiest method used to find the resultant vector of two or more than two vectors.