# be3

## What is an Electric Potential?

Electric potential of a system of charged particles at a point P is defined as work done in moving those charges from reference point to point P divided by total charge of system of particles. The reference point is generally taken to be infinity or some large chunk of neutral body such as earth.

(Or)

Electric potential at a point P is defined as the work done in moving unit coulomb charge from infinity point free of electric fields to point P. Electric potential is measured in terms of volts. It is also called absolute potential and is denoted by V. It is a scalar quantity. Electric potential of a point varies with the choice of reference point w.r.t which potential is measured.

Electric potential Va = W/Σq

## What is Potential Difference?

Potential difference between two points A and B is defined as work done in moving one coulomb charge from point A to B. Alternatively it is understood to be difference of absolute potential of point A and B. It is denoted by VAB. If VA and VB are the electric potentials at points A and B with respect to common reference point (mostly this is taken to be ground i.e. ground is assumed to be at zero potential) then the potential difference between points A and B is given by

VAB = VA – VB

Potential difference between points is invariant w.r.t the choice of reference point.

## What is a Transit time of an Electron between two electrodes?

It is the time taken for an electrode to travel from one electrode to another. Electron since a negatively charge particle travels from low potential to high potential in the direction opposite the electric field direction. Assume a uniform electric field E between two electrodes with spacing between them equal to d then the transit time of electron is given by

T = ($\sqrt{2*d*m/(E*q)}$)

where m and q are mass and charge of electron.

## What is an Electron Volt eV?

It is the defined as the work done in moving an electron through a potential difference of one volt. Typically all the energies involving electron are specified in electron volts for simplicity and ease in analyzing. One electron volt is equal to 1.6*10-19 joules. It can be deduced as follows, the work done in moving a charged particle with charge q from point A to point B whose potentials w.r.t. ground are VA and VB is given by

W = q*( VA – VB), with q=1.6*10-19 coulomb and VA – VB = 1 volt this reduces to 1.6*10-19 J which by definition is electron volt.

What is Electric Field intensity (ε)?

Electric field intensity at a point p in space is defined as the force acting on a unit charge particle with the assumption that the unit charge should not disturb the electric field itself but normally that is the case as one coulomb of charge includes 6.25*1018 charged particles with each particle carrying electronic charge i.e. 1.6*10-19 coulombs.

So the test charge used to measure the field should be as small as possible (Note: the smallest charge stable charge in nature is of electron’s).Hence theoretically electric field is defined as force acting on a test charge divided by the test charge itself as the charge tends to zero.

E = F/q as q–>0 C

It is a vector quantity and always starts from positive charge and ends on negative charge.

## What is an Ionization Potential?

The minimum amount of energy required to remove an electron from an isolated atom or molecule is termed as Ionization potential. It is specified in units of electron volts. Example for Hydrogen atom the ionization potential is 13.6 eV.

## What is an electron spin?

An electron in an atom while revolving around the nuclei of atom rotates around itself. The spin of electron is assigned a quantum number known as spin quantum number which can take values of +1/2 and -1/2 for clockwise and anticlockwise rotation.

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