Types and

properties of electricity

Unit-1Class- X

Electricity

• In general terms the electricity can be defined as a form of energy.

• encompasses a variety of phenomena

• resulting from the presence and flow of electric charge

Related important terms

• Electric charge: - property possessed by objects that makes possible to exert electrical force and/ or to respond to electrical force.

• There are two types of electric charges,– Positive and – Negative, (differentiate on the basis of their polarity.)

Related important terms

• A basic unit of electric charge is represented by “e”.

• The value of basic unit of charge is e = 1.6 X 10-19 Coulomb.

• Coulomb is the unit of electric charge.

Related important terms

• Electric current – a movement or flow of electrically charged particles is known as electric current.

• Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current.

Related important terms

• Ampere is the unit of electric current.

• An amp is the amount of electrical current that exists when a number of electrons, having one coulomb of charge, move past a given point in one second. A coulomb is the charge carried by 6.25 x 10 18 electrons.

Electric Current in different States

• There are different states of matter.• In Solid- the flow or movement of charged

particles (electrons) constitutes the electric current.

Electric Current in different States

• In liquid- the flow or movements of ion (positive or negative) constitute the electric current.

• In Plasma- the electric current flows due to both electron and ion.

Electric field

• The space around the charge • in which electrostatic force of attraction or

repulsion can be experienced by any other electric charge.

Electric potential difference

• The electric potential difference is the capacity of an electric field to do work on a electric charge.

• The electric potential difference is typically measured in volts.

Volt

• One volt is defined as the electrostatic difference between two points when one joule of energy is used to move one coulomb of charge from one point to the other.

Electromagnetism

• a fundamental interaction between the magnetic field and the presence and motion of an electric charge.

Static Electricity

• Static electricity is an imbalance of electric charges within or on the surface of a material.

• The charge remains until it is able to move away by means of an electric current or electrical discharge.

Static Electricity

• The phenomenon of static electricity requires a separation of positive and negative charges.

• Static electricity is named in contrast

with current electricity.

Causes of Static Electricity

• Triboelectric effect: In this method the static electricity develops due to friction or contact of objects.

• Piezoelectric effect: In this method the static electricity develops due to mechanical stress on object.

Causes of Static Electricity

• Pyroelectric effect: - In this method heating of object separates the charges to develop static electricity.

• Electrostatic induction: -In this method A charged object brought close to an electrically neutral object causes a separation of charge within the neutral object develops static electricity.

Current Electricity

• The electricity develops due to the flow or movement of charges.

• There are two type of current electricity

– Direct Current electricity

– Alternating Current electricity

Direct Current Electricity

• The current electricity, in which the electrical charges flows in one specified direction with same amplitude, is known as Direct Current electricity.

Characteristic of D.C. Electricity

• Linear wave Characteristic• The Graphical representation

appears very similar to a straight line.

• Amplitude of Voltage– The amplitude of Voltage in D.C.

electricity always remains constant.

Alternating Current Electricity

• The current electricity, in which the direction of movement of electrical charges changes after a definite interval, is known as A.C. electricity.

Characteristic of Alternating Current Electricity

• Sine Wave Characteristics– A "sinusoidal" or "sine wave form"

represents AC power graphically -called sine wave for short. As you look at this sine wave, remember that this apparently stable picture changes 50 times every second. In doing so, we think in terms of averages of current, voltage and any changes in Frequency.

Amplitude

• Amplitude is the maximum value of current or voltage.

• It is represented by either of the two "peaks" of the sine wave. This voltage level is also referred to as the "Peak Voltage," and it can be either positive or negative.

Amplitude

• Positive and negative refer only to the direction of current flow.

• A negative number does not mean that the voltage or current flows are less than "zero," only that the current flows in the opposite direction.

Frequency

• The number of times the Sine Wave Pattern Cycle occurs in a second is called the "frequency“.

• Frequency was originally measured in "cycles per second" (CPS).

• The unit of measurement for Frequency is called "Hertz," in honor of the German Scientist Heinrich Rudolf Hertz (1857-1894).

• In India the frequency of A.C. supply is 50 Hertz.

Voltage in A. C. Electricity

• There are two values of voltage with which we must be familiar.

– Peak – to – peak Voltage and

– Root Mean Square (RMS) Voltage

Peak – to – peak Voltage

• The "peak-to-peak" voltage is the voltage measured between the maximum Positive and Negative Amplitudes on the sine wave. (It is twice of the Amplitude.)

• This value is the maximum voltage available, but it is not all use-able in practical applications.

Root Mean Square (RMS)• This is standard way of measuring and

reporting effective Alternating Current and voltage.

• It is not the "peak"; it is the "average". • The RMS is found by multiplying the Peak

Amplitude by the Square Root of 2 (approximately 0.707).

• This yields the actual, useable voltage. • It is typically represented by a dotted line

drawn across each "peak" near the 70 percent point.