Class 12 CBSE Physics Current Electricity Boards Questions
Here we provide Class 12 physics important notes,board questions and predicted questions with Answers for chapter Current Electricity. These important notes,board questions and predicted questions are based on CBSE board curriculum and correspond to the most recent Class 12 physics syllabus. By practising these Class 12 materials, students will be able to quickly review all of the ideas covered in the chapter and prepare for the Class 12 Board examinations.
2016
Q1
The variation of potential difference V with length l in case of 2 potentiometer virus P and Q is as
shown which one of these will you prefer for comparing emf of 2 primary cells and why ?
solutions
solutions
Q2
Define the term conductivity of a conductor on what factors does it depend?
solutions
solutions
Q3
Shiv had a high tension tower erected on his farmland. He kept complaining to the authorities to
remove its in occupied the last person of his land. His uncle who was a teacher explained to him the
need for erecting these towers for efficient transmission of power. As Shiv got convinced and
realized its significance and stops complaining
Based on the above paragraph
Answer the following questions :
(i) why is it necessary to transport power at high voltages
(ii) A low power factor implies large power loss . Explain
(iii) Write the 2 values displayed by Shiv and his uncle
solutions
Answer the following questions :
(i) why is it necessary to transport power at high voltages
(ii) A low power factor implies large power loss . Explain
(iii) Write the 2 values displayed by Shiv and his uncle
solutions
2017
Q4
Nichrome and copper wires of same length and same radius are connected in series. Current I is
passed through them. Which wire gets heated up more ? Justify your answer
solutions
solutions
Q5
(a) The potential difference applied across a given resistor is altered so that the heat produced
per second increases by a factor of 9. By what factor does the applied potential difference change ?
(b) In the figure shown, an ammeter A and a resistor of 4 Ω are connected to the terminals of the source. The emf of the source is 12 V having an internal resistance of 2 Ω. Calculate the voltmeter and ammeter readings
solutions
(b) In the figure shown, an ammeter A and a resistor of 4 Ω are connected to the terminals of the source. The emf of the source is 12 V having an internal resistance of 2 Ω. Calculate the voltmeter and ammeter readings
solutions
2018
Q6
Two electric bulbs P and Q have their resistances in the ratio of 1 : 2. They are connected in
series across a battery. Find the ratio of the power dissipation in these bulbs.
solutions
solutions
Q7
A 10 V cell of negligible internal resistance is connected in parallel across a battery of emf 200 V
and internal resistance 38 Q as shown in the figure. Find the value of current in the circuit
OR
In a potentiometer arrangement for deter-mining the emf of a cell, the balance point of the cell in open circuit is 350 cm. When a resistance of 9 Q is used in the external circuit of the cell, the balance point shifts to 300 cm. Determine the internal resistance of the cell.
solutions
In a potentiometer arrangement for deter-mining the emf of a cell, the balance point of the cell in open circuit is 350 cm. When a resistance of 9 Q is used in the external circuit of the cell, the balance point shifts to 300 cm. Determine the internal resistance of the cell.
solutions
Q8
(a) Define the term ‘conductivity’ of a metallic wire. Write its SI unit.
(b) Using the concept of free electrons in a conductor, derive the expression for the conductivity of a wire in terms of number density and relaxation time. Hence obtain the relation between current density and the applied electric field E.
solutions
(b) Using the concept of free electrons in a conductor, derive the expression for the conductivity of a wire in terms of number density and relaxation time. Hence obtain the relation between current density and the applied electric field E.
solutions
2019
Q9
How does the mobility of electron in a conductor change if the potential difference applied across
the conductor is doubled keeping the length and temperature of the conductor constant ?
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Q10
2 bulbs are rated (P1, V) and (P2, V) if they are connected
(i) in series and
(ii) in parallel across a supply we find the power dissipated in the 2 combination in terms of P1 and P2.
solutions
(i) in series and
(ii) in parallel across a supply we find the power dissipated in the 2 combination in terms of P1 and P2.
solutions
Q11
Using kirchhoff’s rules calculate the current through the 40 Ω and 20 Ω resister in the following
circuit :
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solutions
Q12
What is end error in a meter bridge? How is it overcome? The resistance in the two arms of the metre
bridge are R = 5Ω and S respectively. When the resistance S is shunted with an equal resistance, the
new balance length found to be 1.5 l1 where l1 is the initial balancing length
calculate the value of S.
solutions
solutions
2020
Q13
A potentiometer can measure emf of a cell because
a) the sensitivity of potentiometer is large.
b) no current is drawn from the cell at balance.
c) no current flows in the wire of potentiometer at balance.
d) internal resistance of cell is neglected.
solutions
a) the sensitivity of potentiometer is large.
b) no current is drawn from the cell at balance.
c) no current flows in the wire of potentiometer at balance.
d) internal resistance of cell is neglected.
solutions
Q14
Two resistors R1 and R2 of 4 Ω and 6 Ω are connected in parallel across a battery. The ratio
of power dissipated in them, P1 : P2 will be
a) 4 : 9
b) 3 : 2
c) 9 : 4
d) 2 : 3
solutions
a) 4 : 9
b) 3 : 2
c) 9 : 4
d) 2 : 3
solutions
Q15
(a) Two cells of emf E1 and E2 have their internal resistances r1 and r2 , respectively. Deduce an
expression for the equivalent emf and internal resistance of their parallel combination when
connected across an external resistance R. Assume that the two cells are supporting each other.
(b) In case the two cells are identical, each of emf E = 5 V and internal resistance r = 2 Ω, calculate the voltage across the external resistance R = 10 Ω.
solutions
(b) In case the two cells are identical, each of emf E = 5 V and internal resistance r = 2 Ω, calculate the voltage across the external resistance R = 10 Ω.
solutions
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