A

 

• Fig. Light reflecting from inside a cup .
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• ABERRATION -  Distortion of an image due to unequal bending of different coloured light.
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Caustic curve formed in a cup of tea. 


When the parallel light reflects from the inside of a tea cup you can see this curve.


 This is called   spherical aberration.


•  A - Symbol for the unit Ampere in electricity.
•  Ar - Relative atomic mass.
•  α - Symbol for acceleration.

•  AC or ac. = Alternating current.  This is the type of current supplied to houses. The flow of current changes 50 times in one second. It is called 50Hz.
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• ABSOLUTE ZERO  -The lowest possible temperature.  -273° C.   or  0. Kelvin According to Kinetic theory all molecular vibrations should cease at this point.  But it has been now shown that molecules could still possess some energy.

• ABSOLUTE TEMPERATURE - Thermo dynamic temperature . Celsius temperature can be converted to Absolute by adding 273.
• ACCUMULATOR - A battery that can be charged when discharged such as a lead acid car battery.
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• ARCHEMEDES PRINCIPAL.

Any object, totally or partially immersed in a fluid, gets an upthrust  equal to the weight of the fluid displaced by the object.

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• ATOM
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Smallest part of an element which is made up of sub atomic particles.   The lightest atom, Hydrogen is made up of a positively charged particle called a proton and a negative particle called an electron orbiting around it at quite a distance .


Fig. Ernest Rutherford model of the atom.

• ATMOSPHERIC PRESSURE.

This is the pressure due to the envelope of air surrounding the Earth.

Fig. Aneroid Barometer.


This has to be measured by using a Barometer. Mercury barometer and the Aneroid barometer are the two common types.
The determination of this is crucial for weather forecasting.
The normal atmospheric pressure at sea level is 103360 Pascals. Sometimes this is given in a unit called a ‘bar’.   1 bar = 105 Pa.

 This principle states that an increase in the speed of a fluid causes a reduction in pressure. This is made use of in many sprayers.

Low pressure caused by the movement of air causes the liquid to rise.

These are the negatively charged rays coming out of radioactive substances. They really consist of fast moving electrons.

•  Bose-Einstein condensates  .

Satyendra Nath Bose.Indian (1894-1974) predicted the existence of a 5th state. Eric Cornell and Carl Weiman cooled a sample of rubidium to within a few degrees of absolute zero. Then the molecular vibrations ceased and division into atoms disappeared and formed into a super atom. This condition exhibits the properties of super fluids.

           C

    This is the ability of a capacitor to acquire a charge.  Unit of capacitance is Farad.  If a capacitor can hold one coulomb of charge when a voltage of 1V.  is applied the capacity would be 1 Farad. (F)

Capacitance depend on the area and nature of the plates, the gap between the plates and the material (dielectric) in between.

Movement of an object around a fixed centre. It may be uniform or varying. Even if the speed of the object is the same the velocity will not be the same as the direction is changing. As the velocity is changing, there has to be an un balanced force acting.  This will be towards the centre and is called the Centripetal force.

Convection currents occur in liquids and gases. In the case of a fire hot gases expand and rise due to decrease in density. This is the reason why the flames try to go upwards. Cooler air from the surrounding comes to fill the gap.

A substance that can easily transfer an electric current is described as a good conductor.

Similarly a substance that can transmit heat becomes a good conductor of heat.

Usually metals or good conductors of heat and electricity. 

(Opposite = Insulator)

• CRITICAL  ANGLE  click Light-nature,

Mass of a unit volume. Usually given as grams per cubic centimetre or  per litre. The maximum density of water is 1g/cm³

        Formula:-              Density =  Mass / Volume.       

                                 That is:  D =M/V

Temperature at which air becomes saturated with water vapour present.

The spreading of a wave when it reaches an edge or an aperture.

Random motion of molecules specially in a gas. The smell of a flower spreads due to the diffusion of molecules from the flower.

• DEVIATION 

Angle of deviation This is the change of direction due to refraction as shown below.

• DIODE

A device that allows the current to flow only in one direction; really an electric valve. If the current is reversed in this circuit the bulb will not light.

LED is a light emitting diode.

DISPERSION

the separation of white light into colours or of any radiation according to wavelength.

• DISPLACEMENT

This is a length measure considering the direction. It is a vector quantity. Go to velocity.

• DIVERGING RAYS

          A beam of rays may be parallel, diverging (spreading) or meet at a point (Converging) 

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• DOPPLER EFFECT

Please click Wave propertiws.

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• DRY CELL

Allmost all kinds of dry cells are adaptations of the Leclanche's cell.  He used Carbon (graphite) and zinc as electrodes and a solution of ammonium chloride as the electrolyte.

As dry cells cannot have a liquid they use a paste keep the electrolyte moist.

This a ration to compare useful work obtained as to the total work done.

Efficiency =  Useful work / Total work

This can  also be  used to compare energy.

This ratio multiplied by 100 gives the Efficiency percentage.

Electric current

This is the flow of electrons in a conductor. The electrons move from the negative terminal to the positive terminal but it is the convention to say that the current flows from positive to negative.

The current is measured in Amperes while the electrical pressure is given in Volts.

ii.    Direct current DC-This is the current we get from a cell or a battery. Current flows in one direction.

iii.    Alternating current AC-The current supplied to houses is of this nature. It reverses the direction of flow 50 times per second.  This is described as 50 Hertz.

iv.    Common Symbols used in Electrical Circuits.

Ohm’s Law

The current flowing through a conductor is directly proportional to the potential difference (Voltage) applied across the two ends, provided the conditions such as temperature remains the same.

1.    This equation is derived from Ohm’s law.

Fig. Circuit for an electric bell.

For an account of this click
Electro magnetism.

1.Chemical Energy

This is energy absorbed or given out during a chemical change.

Examples :-  1.Burning releases stored up chemical energy as heat and light. Electrical energy passed to a car battery stores it as chemical energy.

2.Radiant Energy

Rays and waves that can radiate in space.

Examples:-   1. Electromagnetic waves ( light, TV waves, X rays etc.)

                    2. Energetic particles from Radioactivity  as from radium

3.Electrical energy

Electric current is a rapid flow of electrons.

Objects can get electrically charged. ( such as the clouds which release the energy in the form of lightening)

4.Atomic energy

Energy stored up in the nucleus of an atom.

Examples :-

1. In the case of the atomic bomb, energy obtained by the breaking up of the nucleus of Uranium.

5.Mechanical energy =

This group includes, kinetic energy, potential energy and vibrational energy.

• ELECTROMAGNETIC WAVES.

Common properties of these .

a. They travel at the highest velocity attainable. 300.000 km /second. (3 x10 ⁸ ms^-1)

b. They can travel in a vacuum.  

The change in enthalpy is related to a change in internal energy          

  

h=U+PV

                        

(U) and a change in the volume (V which is multiplied by the constant pressure of the system.

h = Plank's constant.

       

Muscular forces:-   Push, pull, kick etc.

Attractions:-          Electrical, Magnetic, Gravitational.

Repulsions:-          Electrical and Magnetic

Elastic forces:        Reaction forces,(Support force)  Friction.  

Boyle’s Law

Robert Boyle introduced this in 1662.

In a closed system at constant temperature the volume of a fixed mass of gas is inversely proportional to the pressure.

This results in the equation

Pressure 1 X Volume 1 =  Pressure 2 x Volume 2    

                         P₁V₁ = P₂ V₂

Charles’ Law

The volume of a fixed mass of a gas is directly proportional to the Absolute temperature at constant pressure.

• g =  Symbol for gram.

g =  Acceleration due to Force of gravity.  equal to 9.8 ms-2.

Avogadro’s Law - Equal volumes of different gases at the same temperature and pressure  have an equal number of molecules.    V∝n

GALVANIC CELL-  Luigi Galvani (Italy) was an 18th Century biologist . While he was dissecting a frog his scalpel touched a piece of brass. The leg twitched. Further experiments showed that the procedure generated an electric current.  He called it animal electricity.

This was the first instance of getting electricity from a chemical change.

Today even a tiny current developed between some impurity such as carbon in iron when connected by a drop of rain water generates c current it is called   a Galvanic cell.

GAMMA RAYS - Refer electromagnetic Waves. The wave length  10 –13 to  10-12  m.

• GEIGER COUNTER

This is a simple device to detect radio activity.When the rays enter through the mica window gas molecules get ionized. These ions will conduct electricity and current can be detected by the meter.

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A Mnemonic to remember the Eras

Camels often sit down carefully

^{Cambrian  Ordovician  Silurian  Devonian}    Carboniferous

          Perhaps their joints creak.

              ^{Premium  Triassic  Jurassic  cretaceous}

                     Possibly early oiling might.

                           ^{Palaeocene  Eocene  Oligocene  Miocene}

                                          Prevent premature harm.

                                                                     ^{Pleistocene  Pliocene  Holocene}

What is heat ?We can use heat to get work done; and as such it is a form of energy. Electricity is the movement of electrons. Kinetic energy is due to the movement of matter. What is the nature of Heat?

Heat is also a kind of Kinetic energy. It is the Kinetic energy present in the molecules. In a gas the molecules are in rapid motion. So they have translational k.e. In a liquid state also they show some movement. Even in a solid block molecules are not quiet but they vibrate.

The temperature depends on the state of movement. If the vibrations have a high amplitude or a high speed then the temperature will be high. Kelvin temperature has taken this factor seriously.

Heat Transfer

Heat always flow from a hot body (higher temperature) to a cooler body. There are three methods by which this can occur.

1.      Conduction:  In solids molecules are packed close to each other. Vibration of a molecule can disturb the neighboring molecules.  Passing of kinetic energy in this manner is ‘conduction’ While metals are good conductors of heat non metals and liquids (except mercury) are poor conductors. Gases do not conduct at all and referred to as heat insulators.

2.      Convection:-  In a candle flame, the wax vapour combines with oxygen releasing heat. (Chemical energy transferred to heat) As the temperature is very high part of the energy escape as light. Some energy emanate as infrared radiation. (Heat waves)  The hot gases formed. Carbon dioxide and steam carry most of the energy, 

  as internal energy. Due to expansion these gases become low dense which enables them to rise vertically. This creates an upward draft that draws air from the surroundings.             

In Convection molecules move in a stream. This can occur only in fluids. ( In solids molecules are not free to move)

3.      Radiation:-  T

his is the escaping of heat as infrared radiation. The Earth gets energy from the sun by radiation. At high temperatures other rays of the electromagnetic spectrum such as light of different colours are also produced. 

This is the product of average force and the time it had been acting.

Impulse = F xt..   Impulse is equal to change in momentum.

 This can be a slope that can facilitate to move heavy equipment to a higher level.

The forces due to an object on an incline. What do you think is the force necessary to stop the ball moving?

This is the reluctance of a mass to change its state of motion.

In the case of rotatory motion it depends on the torque.  Inertia = Torque / angular acceleration.

An ion is an electrically charged particle; a molecule or a radical. Examples H⁺  and OH ^-

When an atom or a molecule loses or gains an extra electron  what results is an negative or a positive ion This process is called ionization.

• Ionization