Electric Charges

Types and Sources of Electric Charge

Two kinds of electric charge – positive negative electrons

protons

http://csep10.phys.utk.edu/astr162/lect/light/bohr.html

Bohr Model of Atomhttp://www.physics.ucla.edu/~dauger/orbitals/

Quantum Mechanical Model

Materials with equal numbers of neg. and pos. charge are said to be electrically neutral.

Electric Charges

Types and Sources of Electric Charge

THANKS BEN!

Ben Franklin actually did a great deal of experimentation in the area of electricity.

However, Ben Franklin worked on the negative and Positive charges a lot. which we are using till now.

Electric Charges

Properties of Electric Charge

• Charge is quantized. • Positive and Negative charges have same magnitude

e = p = 1.6 x 10-19 CSI unit of charge is the Coulomb

• Charge is conserved. only charge will be transferred, but can not be destroyed or made.

Electric Charges

Atoms and Materials

Classification of Materials – Conductors, Insulators, Semiconductors

Conductors

Electrons are free to moveabout the material

Insulators

Electrons are bound to the atoms- can’t move (conduct).

Different elements will have differenttypes of bonds – different strengths.

Electric Charges

Insulators

Free StandingAtoms are randomly oriented

Charge does not actually moveIn/on the insulator – redistributes. Polarizes the material.

Electric CurrentElectric Current

THE ELECTRIC BATTERY THE ELECTRIC BATTERY • A BATTERY is a A BATTERY is a

source of electric source of electric energy. A simple energy. A simple battery contains two battery contains two dissimilar metals, dissimilar metals, called ELECTRODES, called ELECTRODES, and a solution called and a solution called the ELECTROLYTE, in the ELECTROLYTE, in which the electrodes which the electrodes are are partially immersed. partially immersed.

ELECTRIC CURRENTELECTRIC CURRENT

• An electric CURRENT An electric CURRENT exists whenever electric exists whenever electric charge flows through a charge flows through a region, e.g., a simple region, e.g., a simple light bulb circuit. The light bulb circuit. The magnitude of the current magnitude of the current is measured in AMPERES is measured in AMPERES (Amps/A), where(Amps/A), where

• 1 ampere = 1 ampere = 1coulomb/second 1coulomb/second

• I = q / t.I = q / t.

CONVENTIONAL CURRENT vs CONVENTIONAL CURRENT vs ELECTRON CURRENT ELECTRON CURRENT • The direction of CONVENTIONAL The direction of CONVENTIONAL

CURRENT is in the direction in CURRENT is in the direction in which positive charge flows. In which positive charge flows. In gases and liquids both positive gases and liquids both positive and negative ions move. Only and negative ions move. Only negative charges, i.e., electrons, negative charges, i.e., electrons, move through solids and this is move through solids and this is referred to as ELECTRON referred to as ELECTRON CURRENT. For historical CURRENT. For historical reasons, conventional current is reasons, conventional current is used in referring to the direction used in referring to the direction of electric charge flow.of electric charge flow.

OHM'S LAWOHM'S LAW

• The magnitude of the electric current that flows The magnitude of the electric current that flows through a closed circuit depends directly on the through a closed circuit depends directly on the voltage between the battery terminals and inversely to voltage between the battery terminals and inversely to the circuit resistance. The relationship that connects the circuit resistance. The relationship that connects current, voltage and resistance is known as OHM'S current, voltage and resistance is known as OHM'S LAW and is written as follows: LAW and is written as follows:

• I = V/R or V = IR I = V/R or V = IR • The current is measured in amperes, The current is measured in amperes,

the voltage in volts and the resistance the voltage in volts and the resistance in ohms (in ohms ().).

Resistors

Symbol on a schematic diagram

For the color code, the first two colors represent the first two digits in the value of the resistor, the third represents the power of ten that it must be multiplied by, and the fourth is the tolerance.

RESISTIVITY RESISTIVITY: When electric charge flows through a

circuit it encounters electrical RESISTANCE. The resistance of a metal conductor or this opposition property of a conductor is called as resistivity.

ELECTRIC POWER

The rate at which work is done to maintain an electric current in a circuit is termed ELECTRIC POWER.

W = QV. Work is required to transfer

charge through an electric circuit. The work required depends on the amount of charge transferred through the circuit and the potential difference between the terminals of the battery: