Electricity is associated with the charge.

TYPES

1. Frictional electricity
2. Static electricity

ELECTRICITY CURRENT AND CIRCUIT

• A continuous and closed path of an electric current is called an electric circuit.
• Electric current is expressed by the amount of charge flowing through a particular area of cross section of a conductor in unit time.
• If a net charge Q, flows across any cross – section of a conductor in time t, then the current I through the cross – section is

I=Q/t

• The S.I unit of electric charges is coulomb.
• The electric current is expressed by a unit called ampere (A), named after the French scientist.
• When one coulomb of charges flows in one second across any cross section of a conductor, the current in it is one ampere.
• An instrument called ammeter is used measure current in a circuit.

ELECTRICAL POTENTIAL AND POTENTIAL DIFFERENCE

• What makes the electric charge to flow? Ter. Charges do not flow in a copper wire by themselves, just as water in a perfectly horizontal tube does not flow.
• We define the electric path potential difference between points in an electric circuit carrying current as the work done to move a unit charge from one point to the other.
• Potential difference (V) between two points = work done (W)/ charge (O).

V=W/Q

• The S.I Unit of potential difference is volt(V)
• One volt is the potential difference between the two points in a current carrying conductor when 1 joule of work is done to move a charge of 1 coulomb from one point to the other.

OHM’S LAW

• Ohms law state that at constant temperature the steady current (I) flowing through a conductor is directly proportional to the potential difference (V) between its ends.

V α I (or) V/I = Constant

RESISTANCE OF A CONDUCTOR

• It is property f a conductor to resist the flow of the charges through it. Its S.I unit is oh, represented by the Greek letter Ω.
• R=V/I, 1 ohm = 1 volt / 1 ampere.

SYSTEM OF RESISTORS:

Resistors in series

• Resister in series consider three resistors of resistances R₁ R₂ R₃ in series with a battery and a plug key the current through each resistor is the same having value.
• V = V₁ + V₂ + V₃
• Rs= R₁ R₂ R₃
• When several resistors are connected in series the resistance of the combination Rs is equal to the sum of their individual resistances R₁ + R₂ + Combination R₃ and is thus greater than any individual resistances.

RESISTORS IN PARALLEL:

• Consider three resistors having resistances R₁ + R₂ + R₃ Connected in parallel. This combination is connected with a battery and plug key.

• In parallel combination the potential difference across each resistor is the same having a value V. The total current I is equal to the sum of the separate currents through each branch of the combination.

• 1 /R_p = 1 / R₁ + 1R₂ + 1R₃

• Thus the reciprocal of the equivalent resistance of a group of resistance joined in parallel is equal to the sum of the reciprocal of the individual resistance.

HEATING EFFECT OF ELECTRIC CURRENT

• Heating effect of electric current has many useful appliances. The electric laundry iron, electric toaster, electric oven and electric heater are some of the familiar devices which use this effect.

JOULES LAW OF HEATING

• P = V (Q/t) = VI
• For steady current I, the amount of heat H produced in time t is

H=V It

Applying ohm’s law we get H = I² Rt.

• This known as joule law of heating.

DOMESTIC ELECTRIC CIRCUITS

• In our country, the potential differences between the two are 220 V.
• Often two separate circuits are used, one of 15 A current rating for appliances with higher power ratings such as geysers, air coolers, etc.
• The other circuit is of 5 a current rating for bulbs, fans etc. The earth wire which has insulation of green color is usually connected to a metal plate deep in the earth near the house. This is used as  safety measure, especially for those appliances that have a metallic body, for example, electric press, toaster table fan refrigerator, etc.,

ELECTRIC POWER

• The rate of doing work is power. This is also the rate of consumption of energy.  This is also termed as electric power.
• The power P is given by P=VI

(or) p=1² R = V²/R

• The S I unit of electric power is watt(W)
• The commercial unit of electric energy is kilowatt hour (kWh), commonly known as ‘unit’.
• 1 k Wh = 1000 watt x 3600 second

  = 3.6 x 10⁶ watt second

  = 3.6 x 10⁶ joule (J)

CHEMICAL EFFECT OF ELECTRIC CURRENT

Electrolysis – Electro Chemical cells.

• Solutions are called electrolytes and the phenomenon of the conduction of electricity through electrolytes and chemical decomposition is called electrolysis.

Electro chemical cell

• Name :Volta

Born           :18 February 1745

• The cells in which the electrical energy is called from the chemical action are called electrochemical cells.

PRIMARY AND SECONDARY CELLS

Primary Cells:

• The cells from which the electric energy is derived by irreversible chemical reaction are called primary cells.
• The primary cell is capable of giving an emf, when is constituents, two electrodes and a suitable electrolytes, are assembled together.
• The main primary cells are Daniel cell and Leclanche cell.
• These cells cannot be recharged.

Leclanche cells:

• The e.m.f of the cells is about 1.5V

Secondary cells:

• The advantage of secondary cell is that they are rechargeable.
• The one of the most commonly used secondary cell is lead acid accumulator.

Lead – acid accumulator

• In a lead-acid accumulator, the anode and cathode are made of lead and lead dioxide respectively.
• The electrolyte is dilute sulphuric acid.
• The e.m.f of freshly charged cell is 2.2V

SOURCES OF ENERGY

Conventional sources of energy

1.Fossils fuels

• Fossil fuel are non-renewable sources of energy

2.Thermal power plant

• Large amount of fossil fuels are burnt everyday in a power stations to hear up water to produce steam which further runs the turbine to generate.
• The transmission of electricity is more efficient than transporting coal or petroleum over the same distance.

3.Hydro Power plant

• Another traditional source of energy was the kinetic energy of flowing water or the potential energy of water at a height.
• In order to produce hydro electricity – high – rise dams are constructed on the river to obstruct the flow of water and there a by collect water in larger reservoirs.

4.Bio – mass

• Bio-mass has been used as a fuel for a long time.
• When wood is burnt in a limited supply of oxygen, water and volatile materials present in it get removed and charcoal is left behind as the residue.
• Charcoal burns without flames, is comparatively smokeless and has hogher hear generation efficiency.
• Similarly, cow-dung, various plant materials like the residue after harvesting the crops, vegetable waste and sewage are decomposed in the absence of oxygen to give bio-gas.
• Since the starting materials is mainly cow-dung, it is popularly known as ‘go bar-gas’.

5.Wind energy

• The energy output of each windmill in a farm is couple together to get electricity on a commercial scale
• Wind is energy is a environment friendly and efficient source of renewable energy.

NON-CONVENTIONAL SOURCES OF ENERGY

Solar energy

• A black surface absorbs more heart than any other surface under identical conditions.
• Solar cookers and solar water heaters is this property in their working.

• These devices are useful only at certain times during the day.
• This limitation of using solar energy is overcome by using solar cells that convert solar energy into electricity.
• A large number of solar cells are combined in a arrangement called solar cell panel that can deliver enough electricity for practical use.

Nuclear energy

• In a process called nuclear fission, the nucleus of heavy atom (such as uranium, plutonium or thorium), when bombarded with low – energy neutrons, can be split apart into lighter nuclei.
• When this is done a, tremendous amount of energy is released if the mass of the original nucleus is just a little more than the sum of masses of the individual products.
• In a nuclear reactor designed for electric power generation sustained fission chain reaction release energy in a controlled manner and released energy can be used to produce steam and further generate electricity.

Radioactivity:

• The phenomenon of traditional was discovered by Henri Bacquerel in 1896..
• The phenomenon of spontaneous emission of highly penetrating radiation such α, β and γ rays by heavy element having atomic number greater than 82 is called radioactivity and substance which emit these radiations are called radioactive elements.
• The radioactive phenomenon is spontaneous and is unaffected by any external agent like temperature, pressure, electric and magnetic field etc.,

\NUCLEAR FISSION AND NUCLEAR FUSION

1.Nucler fusion:

• In 1939, German scientist Otto Hahn and Stresemann discovered that the process of breaking up of a nucleus of a heavier atom two fragments with the release of large amount of energy is called nuclear fission.
• The fission is accompanied of the release of neutrons. The fission reactions with ₉₂U²³⁵ are represented as
• ₉₂U²³⁵+_on¹   ₅₆Ba¹⁴¹ + ₃₆Kr⁹² + 3_on¹+200 me V

2.Nuclear fusion

• Nuclear fusion is a process of which two are more lighter nuclei combine to form a heavier nucleus.
• The mass of the product is always less than the sum of the masses of individual lighter nuclei.
• According to Einstein’s mass energy relation E= mc² the differences in mass is converted into energy.
• The fusion reaction in hydrogen bomb is ₁H² + ₁H³   ₂He⁴ + ₀n¹ + Energy.

Nuclear Reactivity Advantages

• If a reactor is exactly critical, that is the neutron production is exactly equal to the neutron destruction, then the reactivity is zero.
• If the reactivity is positive, then the reactor is super critical. If the reactivity is negative, then the reactor is subcritical.

Hazards of nuclear energy

• The done and the rate at which the radiation is given and
• The part of body exposed to it. The Damage may be either pathological or genetic.
• The radiation exposure is measured by the unit called roentgen (R). One roentgen is defined as the quantity of radiation which produces 1.6 x 10¹² pairs of ion in 1 gram of air.
• Safe limit of receiving the radiation is about 250 mille roentgen per week.
• Radioactive materials are kept in thick-walled lead container.
• Lead aprons and lead gloves are used while working in hazardous area.

MAGNETISM

Magnetism

• Magnet attracts pins, iron pieces and iron particles in sand.
• Cranes are used to lift heavy iron loads.
• Powerful magnets are used in cranes.
• Powerful electromagnets are used to operate electromagnetic trains, lifts and escalators.
• In early days Chinese navigators used magnets to find the direction.
• The magnetite’s are the natural magnets.
• They are called as magnetic stones.
• Natural magnets do not have definite shape.
• When a magnet is freely suspended, it always comes to rest in north-south direction.
• That is why they are called as leading stones or load stones.
• The poles of a magnet are easily found by freely suspending the magnet as shown in the diagram.
• A freely suspended magnet always comes to rest in north-south direction after being disturbed.
• North seeking pole is called north pole.
• South seeking is called south pole.

Attraction and repulsion

• Like poles repel each other.
• Unlike poles attract each other.
• Let us know learn about electromagnetic train.
• In France it is called as flying train.
• It does not require diesel, petrol or any other fuel.

SCIENCE TODAY – ENERGY FROM SEAS

Tidal energy

• Tidal energy is harnessed by constructing a dam across a narrow opening to the sea. A turbine fixed at the opening of the dam converts tidal energy to electricity
• As you can guess, the locations where such dams can be built are limited.

Wave energy

• The kinetic energy possessed by huge wave near the sea – shore can be trapped in similar manner that generates electricity.

Ocean thermal energy

• The water at the surface of the sea or ocean is heated by the sun while water deeper sections is relatively cooled.
• This difference in temperature is exploited to obtain energy in ocean – thermal – energy conversion plants.

MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT

          A current carrying wire has its magnetic effect around it, which can exert a magnetic force on a moving charges. If a current carrying wire is wound on a soft iron bar, it becomes strongly magnetized.

MAGNETIC FIELD AND MAGNETIC LINES OF FORCE:

• The region surrounding the magnetic, in which the force of the magnet can be detected, is said to have a magnetic field.
• The lines along which the iron filling align themselves represent magnetic lines of force.
• Magnetic field is quantity that has magnitude and direction.
• By convention that the field lines emerge from the north pole and merge at the south pole as shown inside the magnet.
• The magnetic fields lines are closed curves No two fields-lines are found to cross each other.

MAGNETIC FIELD DUE TO CURRENT CARRYTING CONDUCTOR

• The direction of magnetic produced by the electric current depends upon the direction of flow current.

MAGNETIC FIELD DUE TO CURRENT STRAIGHT CONDUCTOR

• The magnitude of the magnetic field produced at given point increases as the current through the wire, increases.
• Thus the magnetic field produced by the given current in the conductor decreases as the distance from it increases.

MAGNETIC FIELD DUE TO CURRENT CARRYING CIRCULAR LOOP

• Magnetic field produced by a current – carrying straight wire depends inversely on the distance from it.
• Similarly at every of current carrying circular loop, the concentric circles representing the magnetic field around it becomes larger and larger as e move away from the wire.

FORCE ON A CURRENT CARRYING CONDUCTOR IN A MAGNETIC FIELD

• French scientist Andre Marie Ampere suggested that the magnet must also exert an equal force on the current carrying conductor.
• The force due to current carrying conductor can be demonstrated through the following activity.
• The direction of force on the conductor depends upon the direction of current and the direction of magnetic field.

FLEMMING LEFT HAND RULE

• Stretch the thumb, fore finger and middle finger of your left hand such that they are mutually perpendicular.
• If the forefinger point in the direction of magnetic field and the middle finger point in the direction of current, then the thumb will point in the direction of motion of the force acting on the conductor.

ELECCTRIC MOTOR

The commercial motors use

1. An electro magnet in place of permanent.
2. Large number of turns of the conducting wire in the current carrying coil, and

• A soft iron core on which the coil is wound. The soft iron core, on which the coil is would, plus the coil, is called an armature.  This enhances the power of the motor.

ELECTROMAGNETIC INDUCTION

• Faraday in 1831 discovered that an electro motive force is produced in a circuit whenever the magnetic flux linked with a coil changes.
• The induced emf will cause a current to flow through the conductor. Such current known as induced current.
• Faraday made an important breakthrough by discovering how a magnet can be used to generate electric currents.

FARADAY’S EXPRERIMENT

• The direction of the induced current can be found using Fleming’s right hand rule.
• Stretch the thumb, forefinger and middle finger of right hand so that they are perpendicular to earth other.
• If the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of conductor, then the middle finger will show the direction of induced current.

ELECTRIC GENERATOR

• The phenomenon of electro magnetic induction is employed to produce large current for use in homes and industry.
• In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity.
• Current which changes direction after equal intervals of time, is called an alternating current(AC). This device is called an AC generator.
• To get direct current (DC), a split ring type commentator must be used with this arrangement.
• Thus a unidirectional current is produced. The generator is thus called a DC generator.
• An important advanced of AC over DC is that electric power can be transmitted over long distances without much loss of energy.

SCIENCE TODAY

CHANDRYAAN

• Mylswamy Annadurai born on 2^nd july 1958 is a household name in this part of the country
• Currently Annadurai serves as the Project Director of Chandrayaan-1 and Chandrayaan -2
• Chandrayaan 1 is an moon-traveler or moon vehicle.
• Chandrayan operated foe 312 days and achieved 95% of its planned objectives.
• The discovery of wide spread presence of water molecules in lunar soil.
• Chandrayaan’s Moon Mineralogy Mapper has confirmed that moon was once completely molten.
• European Space Agency Payload-Chandrayaan-1 imaging X-ray spectrometer (CXIS)-detected more than the two dozen weak solar flares during the mission.
• The terrain mapping camera on board chandrayaan-1 has recorded images of the the landing site of US-space craft Apollo-15, Appolo-11
• It has the provided high resolution spectral data on the mineralogy of the moon
• Lunar Laser Ranging Instrument (LLRI) covered both the Lunar Poles and additional lunar region of interest.
• The X ray signature of aluminium, magnesium and silicon were picked up by the CXIS X rays camera.
• The Bulgarian payload called Radiation Dose Monitor (RADOM) was activated on the day of launch itself and worked till the mission end.
• More than 40000 imaged have been transmitted by Chandrayaan camera in 75 days.
• The Terrain Camera Acquired imaged of peaks and craters. The moon consists of mostly of craters.
• Chandrayaan beemed back its first images of the Earth in its entirety.
• Chandrayaan-1 has discovered large caves on the lunar surface that can act as human shelter on the moon.

CRYOGENIC TECHNIQUES

• The word cryogenics terms from Greek and means “The production of freezing cold”.
• The field of cryogenics advanced during world war-2
• Cryogenic like liquid nitrogen are further used for specially chilling and freezing application.
• ROCKET
• Cryogenic fuels mainly liquid hydrogen has been used as rocket fuel.

(ii)Magnetic Resonance Imaging (MRI)

• MRI is used to scan inner organs of human body by penetrating very intense magnetic field.
• The magnetic field is generated by super conducting coils with the help of liquid helium.

(iii)POWER TRANSMISSION IN BIG CITIES

• Liquefied gases are sprayed on the cab le to keep them cool and reduce their resistance.

(iv)FOOD FREEZING

• Cryogenic gases are used in transportation of large massed of frozen food, when very large quantity of food, must transported to region like war field, earthquake hit regions etc., they must be stored for.

(v)VACCINES

• The freezing of biotechnology products like vaccines require nitrogen freezing systems.

SPACE STATION:

• A space station is an artificial structure designed for humans to live and work in outer space for a period of time.
• The only space stations are Almaz and Salyut series, Sky lad and Mir.
• Salyut and Skylab have been “monolithic”
• They were constructed and launched in one piece, and then manned by a crew later.
• The second group, Mir and the International Space station (ISS) have been modular, a core unit was launched and additional
• The people’s Republic of China is expected to launch its space station named Tangoing 1, in the first half of 2011. This would make China the third country to launch a space station.