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What is current density ?

The amount of electric current flowing per unit cross sectional area of a material. It is a vector quantity. In SI units, the electric current density is measured in amperes per square metre.

More the current in a conductor, higher will be the current density. the current density alters in different parts of electrical conductor and the effect takes place with alternating currents at higher frequencies.

Current density is a vector quantity having both a direction and a scalar magnitude.

Current Density Formula:
The formula for Current Density is given as,
J = I / A
Where,
I = current flowing through the conductor in Amperes
A = cross sectional area in m2.
Current density is expressed in A/m2.

Surface current density vs. Volume current density

Surface is current flowing over the surface of the wire.

Volume is through the entire volume of the wire.

https://www.youtube.com/watch?v=QJsAWRWvb7E

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Kashish Raimalani, Laveena Thakur, Prateek Wadhavkar, Kunal Purswani

Electric current (I) is defined as the rate of flow of charge(Q) through a conductor.

Therefore, I=Q/t

While a random movement of electrons always takes place, net movement of electrons is nearly always zero. However, when an electric field is induced, the net movement of charge, or current, is induced as well. The induced flux in the electric field is directly proportional to an increase in the electric current in a conductor. Hence for no change in the electric field, there is no flowing charge.

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Mehak, Kunal, Jay and Angelina
The potential difference between two points in an electric circuit is the work done when a coulomb of charge passes between the points. In simpler words, it is the energy dissipated per unit change. You can calculate the size of a potential difference using this equation:

V = W ÷ Q

·       V is the potential difference in volts, V

·       W is the work done (energy transferred) in joules, J

·       Q is the charge in coulombs, C

Potential difference is measured in volt (V). It was named after the renowned great scientist Mr. Alessandro Volta. One volt is equivalent to one joule per coulomb. It is measured used a voltmeter. A voltmeter needs to always be connected in parallel.

When there is potential difference, there must be an electric field.

Bibliography: http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/electricity/circuitsrev5.shtml

http://www.physicsclassroom.com/class/circuits/Lesson-1/Electric-Potential-Difference

https://en.wikibooks.org/wiki/IB_Physics/Electric_Currents

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View:
https://www.youtube.com/watch?v=-Rb9guSEeVE

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The Joule is a unit of energy in the SI system. Energy is measured in joules. However, joule is very large unit while dealing with electrons and other tiny particles. Hence, electron volt is used while dealing with smaller particles like electrons.

Electron volt is defined as the amount of energy one electron acquires by accelerating (from rest) through a potential difference of one volt. Hence, one electron volt is equal to elementary charge (1.60217657 × 10-19 coulombs (C)) multiplied by one volt. It can be written as

eV = (1.60217657 × 10-19 C) (1V)

Therefore, 1eV = 1.60217657 × 10-19 J.

The work done on the charge is given by the charge times the voltage difference

It is a convenient energy unit, particularly for atomic and nuclear processes.