Current Electricity Test Paper 04 - Class 12

 Page 1


CBSE TEST PAPER-04 
CLASS - XII PHYSICS (Unit – Current Electricity) 
1. If a wire is stretched to double of its length. What will be its new resistivity? [1] 
2. Name any one material having a small value of temperature coefficient of
resistance. Write one use of this material?
[1] 
3. Figure shows a piece of pure semiconductor S in series with a variable resistor
Rand a source of constant voltage V. Would you increase and decrease the value
of R to keep the reading of ammeter (A) constant, when semiconductor S is
heated ? Give reasons.
_
+
[2] 
4. The variation of resistance of a metallic conductor with temperature is given in
figure.
(a) Calculate the temperature coefficient of resistance from the graph.
(b) State why the resistance of the conductor increases with the rise in
temperature. 
[3] 
Page 2


CBSE TEST PAPER-04 
CLASS - XII PHYSICS (Unit – Current Electricity) 
1. If a wire is stretched to double of its length. What will be its new resistivity? [1] 
2. Name any one material having a small value of temperature coefficient of
resistance. Write one use of this material?
[1] 
3. Figure shows a piece of pure semiconductor S in series with a variable resistor
Rand a source of constant voltage V. Would you increase and decrease the value
of R to keep the reading of ammeter (A) constant, when semiconductor S is
heated ? Give reasons.
_
+
[2] 
4. The variation of resistance of a metallic conductor with temperature is given in
figure.
(a) Calculate the temperature coefficient of resistance from the graph.
(b) State why the resistance of the conductor increases with the rise in
temperature. 
[3] 
5. A circle ring having negligible resistance is used to connect four resistors of
resistances 6R , 6R , 6R and R as shown in the figure. Find the equivalent
resistance. between points A & B
[3] 
6. A battery of emf E and internal resistance r sends a current I 1 and I 2, when
connected to an external resistance of R1 and R2 respectively .Find the emf. and
internal resistance of the battery?
[3] 
7. Find the value of unknown resistance X in the circuit shown in the figure if no
current flows through the section AO. Also calculate the current drawn by the
circuit from the battery of emf.   6v and negligible internal resistance.
[3] 
8. (a)  Obtain ohm’s law from the expression for electrical conductivity.
(b) A cylindrical wire is stretched to increase its length by 10% calculate the
percentage increase in resistance? 
[3]