Magnetic effect of electric current, part 1, Sure questions , SSLC Physics

SSLC PHYSICS SURE QUESTIONS- PART 2 LIGHTING EFFECT OF ELECTRICITY

SSLC Physics: Exam Sure Questions and Answers, Effects of electric curre...

effects of electric current - heating effect

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effects of electric current:  heating effect

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Why Quantum mechanics?

                                       Quantum Mechanics Basic concepts

Why Quantum mechanics?

Before discussing the Quantum physics we have to go through Classical mechanics
Fault Concepts of classical mechanics which leads to quantum mechanics
1. According to Newton for every motion there is a reason for it. It is called the cause and effect relationship
2.If you now the exact position and velocity of the moving object we can predict its position in future and past with certainty.
3. According to classical theory there is no uncertainty in any phenomenon, it is the determinism of classical mechanics
4.Energy can be transfered from one place to another either  as particle or as waves.These forms cannot merge together
5.Measurement is perfect if the working condition of the measuring device is perfect. The error in measurement take place only by the fault of measuring device

solvay conferences
Einsteens quantum statistical interpretation
coppen hagen interpretation
maxwells kinetic theory of gases
boltmans statistical mechanics
probability theory of gases
black body radiation
ultraviolet catastrophe
photo electric effect
bright line light spectra
emission spectra
absorption spectra
rutherford atom model
bhor atom model
sommerfield atom model
paulis exclusion principle
de broglie dual wave

                       PHOTO ELECTRIC EFFECT

The emission of electrons from the surface of the certain substances mainly metals, when they are illuminated by electro magnetic waves.

The alkali metals like lithium, sodium, potassium emit electrons when exposed with visible light. Ultra violet rays eject electrons from Zinc and magnesium. Infra red rays emitted photo electrons from caesium. This effect is first discovered by Heinrich Hertz

FRAME OF REFERENCE,LIMITATIONS OF NEWTONS LAW,CARTESIAN COORDINATE SYSTEM,fictitious force

MOTION AND REST

If the position of a body changes with time ,the body is in the state of motion. If the position of the body does not changes with time it is said to be at rest.

ABSOLUTE MOTION

when the motion of a body is observed with respect to a point which is stationary in space is called absolute motion. But in universe no point is stationary. So absolute motion is an imaginary concept.

MOTION IS RELATIVE ie we can define motion relative to other bodies.

FRAME OF REFERENCE

A tree on the ground is at rest relative to earth. But it is in motion relative to sun.So in order to describe motion we first select one frame

         If we imagine a co ordinate system attached to a rigid body and we describe the position of any particle in space relative to it. Then such a co-ordinate system is called frame of reference. for location of the object the position vector are drawn from the origin of co-ordinate system. The origin may coincide with the position of observer or not But an observer uses a frame of reference which is stationary relative to him.

CARTESIAN COORDINATE SYSTEM

For the location of an event in a frame of reference we require its position and time of occurrence. Therefore 4 coordinates are required(x,y,z,t). It is called space-time frame of reference.We select a frame of reference in which the motion is easy to describe.

Example

1)A man sitting in the train throw a ball vertically upwards, with respect to an observer sitting in train the path of ball is vertically straight line. But an observer outside the train the path of ball is parabolic.

 The frame of observer in train is simple with describing the motion of the ball

2)To describe the motion of planets in the frame with respect to earth is very complicated. But the frame situated in on sun is very simple. Now the motion of all planets are circular

3)Motion of a point on a slow moving wheel of a car. If the frame is on the center of wheel, then the motion of point is circular. But frame situated on earth the motion of point is cycloid.

LIMITATIONS OF NEWTONS LAW

According to Newton's first law a body continues its state of rest or uniform motion in a straight line unless compelled by an external force.

This law violates when the observer is in an accelerated frame. Suppose if the object is at rest and the observer is on an accelerated frame, he can observe the object with negative acceleration and he at rest. A fictitious force is acting on the body.

   So Newton introduced an inertial frame , which is not accelerated relative to fixed stars and his laws are valid only in inertial frame.

    

LAWS OF THERMODYNAMICS

SYSTEM & SURROUNDINGS

System refers to the part of universe chosen for our study

The portion of universe excluded from the system is called surroundings

Types of systems

open system

A system which can exchange both matter and energy  with its surroundings is called open system.

Eg: hot coffee kept in a open vessel

Closed system

A system which can exchange  energy but not matter is  with its surroundings is called open system.

Eg: hot coffee kept in a closed vessel with conducting walls

Isolated system

 A system which can neither exchange  matter or energy  with its surroundings is called open system.

Eg:hot coffee kept in a thermos flask

  STATE FUNCTION & PATH FUNCTION

Property of a system depends only on the state of system and not depend on the path along which that state is attained is called state function

Eg:Pressure , volume , temperature

Property of a system which depends on the path along with the state is attained

is called path function

Eg: work, heat

INTENSIVE & EXTENSIVE PROPERTIES

Properties which are independent of amount of matter present in a system is called intensive properties

Eg:Pressure , viscosity , temperature

Properties which are dependent of amount of matter present in a system is called intensive properties

Eg: Mass, Volume , Energy

ENERGY OF A SYSTEM

Energy of a system is its capacity to do work. When a system does work, its energy is reduced and when work is done on a system its energy increases.

ADIABATIC & ISOTHERMAL PROCESS

A process in which no heat enters or leaves the system is called an adiabatic process. In such process the system is completely insulated from the surroundings.

An isothermal process is one which the temperature of the system remains constant throughout.In such a system energy can exchange to surroundings

ENDOTHERMIC & EXOTHERMIC PROCESS

process which liberates energy as heat is called an exothermic process

process which liberates energy as heat is called an exothermic process

REVERSIBLE PROCESS & IRREVERSIBLE PROCESS

A reversible process is one which is conducted infinitesimally slowly such that at every stage the driving force is only infinitesimally greater than the opposing force.. Such a process can be reversed by increasing the opposing force by an infinitesimal amount.
A process in which the driving force at any stage is greater than the opposing force is called an irreversible process.
All natural forces are irreversible.
INTERNAL ENERGY OF A SYSTEM(E)
The internal energy is the sum of total energies associated with the translational,rotational, vibrational,electronic, and nuclear motions at the molecular level as well as potential energy of interaction between constituent particles.

ENTHALPY(H)

Enthalpy is the sum of internal energy and pressure volume energy.
H=E+PV

THE ZEROTH LAW

Two systems that are both in thermal equilibrium with a third system are in thermal equilibrium with each other

FIRST LAW OF THERMODYNAMICS

Energy can neither be created nor destroyed it  may be converted from one form to another

SPONTANEOUS PROCESS

A  process which has a natural urge to take place by itself under a given set of conditions.

ENTROPY

Entropy is a measure of disorder or randomness in a system.

Greater the entropy greater the disorder

SECOND LAW OF THERMODYNAMICS

The entropy of the universe remains constant in a reversible process where as it increases in a irreversible process

GIBBS FREE ENERGY

It is the maximum amount of energy available with a system that can be converted into useful work or free energy the measure of the capacity of a system to do useful work
G=H-TS(Gibbs -Helmholtz equation)
A process should be spontaneous only if the free energy change is negative.

 JOULE THOMSON EFFECT

When a gas under high pressure is allowed to explain under adiabatic conditions through a porous plus in to a region of low pressure, there occur  a change in its temperature. When a gas expands adiabatically some work is done by the gas to overcome the van der waals  force of attraction between molecules.This is done at the cost of the kinetic energy of the gaseous  molecules.Then the internal energy decreses the temperature decreases

PRIMARY CELLS -voltaic cell,daniel cell

                          PRIMARY CELLS

Cells which gives the electrical energy by irreversible chemical reaction is called primary cell .primary cells are not rechargeable.

VOLTAIC CELL

A voltaic cell consist of of copper and zinc electrodes dipped in dilute sulphuric acid.The positive charges accumulate on the copper electrode and negative charges on the zinc electrode.This is because the electrolyte decomposes in to H ions and Sulphate ions. The negatively charged sulphate ions move towards Zn and Zn loses two electrons and become ZnSO4 .Positively charged Hydrogen ions move towards Cu and accept two electrons and hydrogen gas is liberated.

When the circuit is closed the Cu is at higher potential and Zn is at lower potential. Current flows from Cu electrodes to Zn electrode in the external circuit. The emf of the cell is 1V.

 DANIEL CELL

Danial cell consist of a copper vessel containing copper sulphate solution. The wall of the vessel is the positive electrode. A porous pot containing dilute sulphuric acid is placed in the CuSO4 solution. The Zinc rod is immersed in dilute sulphuric acid. This is the negative electrode.

The porous pot allows the ions to pass from one solution to other but prevents the mixing of the solutions.Oxidation take place at Zinc rod.The Zinc ions move to the copper sulphate solution through the porous pot and combine with sulphate ion to form zinc sulphate.

Cu ions move towards the copper vessel and are deposited there.The reduction reaction take place

diagram