CBSE Class 12 Physics Chapter-3 Important Questions – Free PDF Download
Free PDF download of Important Questions with Answers for CBSE Class 12 Physics Chapter 3 – Current Electricity 1 Mark Questions prepared by expert Physics teachers from latest edition of CBSE(NCERT) books only by CoolGyan to score more marks in CBSE board examination.
CBSE Class 12 Physics Chapter-3 Important Questions
CBSE Class 12 Physics Important Questions Chapter 3 – Current Electricity
1 Mark Questions
1. If the temperature of a good conductor decreases, how does the relaxation time of electrons in the conductor change?
Ans. We know 
When temperature decreases, collision decreases and thus relaxation time increases which in turn decreases the resistivity.
2. If potential difference V applied across a conductor is increased to 2V, how will the drift velocity of the electron change?
Ans. 
Double the P.D means drift velocity gets doubled.
3. What is the value of current I at O in the adjoining circuit?
Ans. i = 5 + 3 – 2 – 7 + 8
i = 16 – 9
i = 7A
4. State one condition for maximum current to be drawn from the cell ?
Ans. Since
for maximum current, internal resistance should be Zero.
5. Resistivites of copper, silver and manganin are 
, 
and
. respectively which of these is the best conductor ?
Ans. For a particular length and area of cross-section, The resistance is directly proportionate to, specific resistance .
silver is the best conductor because its specific resistance is less.
6. Draw the graph showing the variation of conductivity with temperature for a metallic conductor?
Ans. The conductivity decreases with the increase in temperature.
7. If a wire is stretched to double of its length. What will be its new resistivity?
Ans. No change in its resistivity because resistivity depends only on the nature of the material.
8. Name any one material having a small value of temperature coefficient of resistance. Write one use of this material?
Ans. Nichrome, an alloy has small value of temperature coefficient of resistance. It is used for making standard resistance coil.
9. Two wires A and B are of the same metal and of same length have their areas of cross section in the ratio 2:1 if the same potential difference is applied across each wire in turn, what will be the ratio of current flowing in A & B?
Ans. Since R 
If area are in the ratio 2:1 resistance will be in the ratio 1:2.
And I = 
