CBSE Class 12 Physics Current Electricity Frequently Asked Questions

CBSE Class 12 Physics Current Electricity Frequently Asked Questions. There are many more useful educational material which the students can download in pdf format and use them for studies. Study material like concept maps, important and sure shot question banks, quick to learn flash cards, flow charts, mind maps, teacher notes, important formulas, past examinations question bank, important concepts taught by teachers. Students can download these useful educational material free and use them to get better marks in examinations.  Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.

CURRENT ELECTRICITY

1. Two wires ‘A’ & ‘B’ are of the same metal and of the same length. Their areas of crosssection are in the ratio of 2:1. if the same potential difference is applied across each wire in turn, what will be the ratio of the currents flowing in ‘A’ & ‘B’?

2. Explain, with the help of a graph, the variation of conductivity with temperature for a metallic conductor.

3. Draw V-I graph for ohmic and non-ohmic materials. Give one example for each.

4. Explain how does the resistivity of a conductor depend upon (i) number density ‘n’ of free electrons, & (ii) relaxation time‘t’.

6. A cell of emf (E) and internal resistance (r) is connected across a variable external resistance (R) Plot graphs to show variation of (i) E with R (ii) terminal p.d. of the cell (V) with R.

7. Explain how electron mobility changes from a good conductor (i) when temperature of the conductor is decreased at constant potential difference and (ii) applied potential difference is doubled at constant temperature. 

8. Write the mathematical relation between mobility and drift velocity of charge carriers in a conductor. Name the mobile charge carriers responsible for conduction of electric current in: (i) an electrolyte, & (ii) an ionised gas.

9. Define drift velocity. Establish a relation between current & drift velocity.

10. Define the term current density of a metallic conductor. Deduce the relation connecting current density ‘J’ & the conductivity ‘s’ of the conductor when an electric field ‘E’ is applied to it.

11. Why do we prefer potentiometer to compare the e.m.f of cells than the voltmeter. Why?

12. State Kirchhoff’s rules of current distribution in an electric network.

13. The variation of potential difference “V’ with length ‘l’ in the case of two potentiometers ‘X’ & ‘Y’ is as shown in figure. Which one of these two will you prefer for comparing ‘emf’s of two cells and why? 

14. Draw a circuit diagram using a metre bridge and write the necessary mathematical relation used to determine the value of an unknown resistance. Why cannot such an arrangement be used for measuring very low resistance?

15. With the help of a circuit diagram, explain in brief the use of a potentiometer for comparison of ‘emf’s of two cells.

16. Prove that the current density of a metallic conductor is directly proportional to the drift speed of electrons.

17. A number of identical cells, n, each of emf E, internal resistance r connected in series are charged by a d.c. source of emf E′, using a resistor R.

(i) Draw the circuit arrangement.

(ii) Deduce the expressions for (a) the charging current and (b) the potential difference across the combination of the cells.

18. Derive the principle of wheatstone bridge using Kirchoff’s law.

19. State Kirchhoff’s rules of current distribution in an electrical network. Using these rules determine the value of the current I in the 1 electric circuit given below.

20. Write the mathematical relation for the resistivity of material in terms of relaxation time, number density and mass and charge of charge carriers in it.Explain, using this relation, why the resistivity of a metal increases and that of semi-conductor decreases with rise in temperature.

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