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."