CBSE Class 12 Physics Current Electricity Notes Set 03

CBSE Class 12 Physics Notes - Current Electricity CBSE,CCE and NCERT students can refer to the attached file. All educational material on the website has been prepared by the best teachers having more than 20 years of teaching experience in various schools. The study material available on our website for all CBSE classes and subjects have been prepared by teachers from all over the country. All study material has been carefully designed keeping into mind the latest CBSE examination trends.  

Class XII: Physics

Ch 3: Current Electricity

Chapter Notes

Top Concepts

1. Current through a given area of a conductor is the net charge passing per unit time through the area.

2. The current density vector gives current per unit area flowing through area ( A) when it is held normal to the direction of charge flow. Note that the direction of is in the direction of current flow.

3. Drift speed, which is the magnitude of this velocity, is enormously small as compared to the thermal speed, which is not a vector and is much larger.

4. When a conducting substance is brought under the influence of an electric field , free charges (e.g. free electrons in metals) moveunder the influence of this field in such a manner, that the current density due to their motion is proportional to the applied electric field.where is a constant of proportionality called electrical conductivity. This statement is one possible form of Ohm’s law.

is called resistance of the material.

in this form, ohm law can be stated as linear relationshipThe potential difference (voltage) across an ideal conductor is proportional to the current through it.

Also, download the notes for electromagnetic waves class 12 in PDF format.

5. Emf (Electromotive force) is the name given to a non-electrostatic agency. Typically, it is a battery, in which a chemical process achieves this task of doing work in driving the positive charge from a low potential to a high potential. The effect of such a source is measured in terms of work done per uni charge in moving a charge once around the circuit. This is denoted by.

6. Metals have low resistivity: Range of  varies from 10–8 Ω m to 10–6 Ω m. Insulators like glass and rubber have high resistivity: Range of  varies from 1022 to 1024 times greater than that of metals. Semiconductors like Si and Ge lie roughly in the middle range of resistivity on a logarithmic scale.

7. Current density j gives the amount of charge flowing per second per unit area normal to the flow.

J = nq vd

where n is the number density (number per unit volume) of charge carriers each of charge q and vd is the drift velocity of the charge carriers. For electrons q = –e. If j is normal to a cross – sectional area A and is constant over the area, the magnitude of the current I through the area is nevd A.

Please refer to the link below for CBSE Class 12 Physics Notes - Current Electricity