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NCERT Exemplar Class 12 Physics solutions chapter 3 is from the point of view of exams. It also gives students an insight on how current flows in working of different types of devices in real life such as conductors. The previous chapters dealt with charges that were considered as at rest, whereas this chapter introduces various concepts relating to steady currents. NCERT Exemplar Class 12 Physics chapter 3 solutions includes the idea of electric energy and power, electric resistivity, and conductivity, along with a detailed explanation of carbon resistors and their colour codes. The concepts discussed in the NCERT Exemplar Class 12 Physics solutions chapter 3 are important from the point of view of board exams as the JEE Main exam. The students can also make use of NCERT Exemplar Class 12 Physics solutions chapter 3 PDF download, for further learning.
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Also see - NCERT Solutions for Class 12 Physics
Question:1
Consider a current carrying wire (current I) in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while the current I remain unaffected. The agent that is essentially responsible for is
A. source of emf.
B. electric field produced by charges accumulated on the surface of wire.
C. the charges just behind a given segment of wire which push them just the right way by repulsion.
D. the charges ahead.
Answer:
b)Question:2
Two batteries of emf and and internal resistances r1 and r2 respectively are connected in parallel as shown in Figure.
A. The equivalent emf of the two cells is between and , i.e.
B. The equivalent emf is smaller than 1.
C. The is given by always.
D. is independent of internal resistances r1 and r2.
Answer:
The correct answer is the option (a)Question:3
A resistance R is to be measured using a meter bridge. Student chooses the standard resistance S to be 100. He finds the null point at . He is told to attempt to improve the accuracy. Which of the following is a useful way?
A. He should measure l1 more accurately.
B. He should change S to 1000and repeat the experiment.
C. He should change S to 3 and repeat the experiment.
D. He should give up hope of a more accurate measurement with a meter bridge.
Answer:
The correct answer is the option (c)Question:4
Two cells of emf’s approximately 5V and 10V are to be accurately compared using a potentiometer of length 400cm.
A. The battery that runs the potentiometer should have a voltage of 8V.
B. The battery of potentiometer can have a voltage of 15V and R adjusted so that the potential drop across the wire slightly exceeds 10V.
C. The first portion of 50 cm of the wire itself should have a potential drop of 10V.
D. Potentiometer is usually used for comparing resistances and not voltages.
Answer:
The correct answer is the option (b)Question:5
A metal rod of length 10 cm and a rectangular cross-section of is connected to a battery across opposite faces. The resistance will be
A. maximum when the battery is connected across faces.
B. maximum when the battery is connected across faces.
C. maximum when the battery is connected across faces.
D. same irrespective of the three faces.
Answer:
The correct answer is the option (a)Question:6
Which of the following characteristics of electrons determines the current in a conductor?
A. Drift velocity alone.
B. Thermal velocity alone.
C. Both drift velocity and thermal velocity.
D. Neither drift nor thermal velocity
Answer:
The correct answer is the option (a)Question:7
Kirchhoff ’s junction rule is a reflection of
A. conservation of current density vector.
B. conservation of charge.
C. the fact that the momentum with which a charged particle approaches a junction is unchanged (as a vector) as the charged particle leaves the junction.
D. the fact that there is no accumulation of charges at a junction.
Answer:
The correct answers are the options (b,d)Question:8
Consider a simple circuit shown in Figure variable resistance R’. R’ can vary from to infinity. r is internal resistance of the battery
A. Potential drop across AB is nearly constant as R’ is varied.
B. Current through R is nearly a constant as R’ is varied.
C. Current I depends sensitively on R’.
D. always.
Answer:
The correct answers are the options (a,d)Question:9
Temperature dependence of resistivity of semiconductors, insulators and metals is significantly based on the following factors:
A. number of charge carriers can change with temperature T.
B. time interval between two successive collisions can depend on T.
C. length of material can be a function of T.
D. mass of carriers is a function of T.
Answer:
The correct answers are the options (a,b)Question:10
The measurement of an unknown resistance R is to be carried out using Wheat stones bridge (see Figure of NCERT Book). Two students perform an experiment in two ways. The first students take and . The other student takes and . In the standard arm, both take . Both find within errors.
A. The errors of measurement of the two students are the same.
B. Errors of measurement do depend on the accuracy with which and can be measured.
C. If the student uses large values of and , the currents through the arms will be feeble. This will make determination of null point accurately more difficult.
D. Wheatstone bridge is a very accurate instrument and has no errors of measurement.
Answer:
The correct answers are the options (b,c)Question:11
In a meter bridge the point D is a neutral point (Figure).
A. The meter bridge can have no other neutral point for this set of resistances.
B. When the jockey contacts a point on meter wire left of D, current flows to B from the wire.
C. When the jockey contacts a point on the meter wire to the right of D, current flows from B to the wire through galvanometer.
D. When R is increased, the neutral point shifts to left.
Answer:
The correct answers are the options (a,c)Question:12
Is the momentum conserved when charge crosses a junction in an electric circuit? Why or why not?
Answer:
As drift velocity is proportional to the electric field, when charge crosses a junction the momentum is not conserved.Question:15
What is the advantage of using thick metallic strips to join wires in a potentiometer?
Answer:
Thick metallic strips have large cross section and thus offer less resistanceQuestion:16
For wiring in the home, one uses Cu wires or Al wires. What considerations are involved in this?
Answer:
The following considerations are made to decide on the wiring:Question:17
Why are alloys used for making standard resistance coils?
Answer:
Because of their low temperature sensitivity and low temperature coefficient of resistance, alloys are used to make standard resistance coils. Also, they have a lower conductivity or higher resistivity, this reduces the length required to make coils.Question:20
While doing an experiment with potentiometer (Figure ) it was found that the deflection is one sided and (i) the deflection decreased while moving from one end A of the wire to the end B; (ii) the deflection increased. While the jockey was moved towards the end B.
(i) Which terminal +or –ve of the cell, is connected at X in case (i) and how is related to ?
(ii) Which terminal of the cell is connected at X in case (ii)?
Answer:
i) As jockey moves closer to B, the galvanometer potential difference decreases. This requires the positive terminal of to be at X.Question:31
(a) Consider the circuit in Figure. How much energy is absorbed by electrons from the initial state of no current (ignore thermal motion) to the state of drift velocity?
(b) Electrons give up energy at the rate of per second to the thermal energy. What time scale would one associate with energy in problem (a)? n = no of electron/volume = , length of circuit = 10 cm, cross-section = A
Answer:
a)· NCERT Exemplar solutions for Class 12 Physics chapter 3 introduces new principles/laws as OHM’s law, Kirchhoff’s rule, etc., which display and govern the flow of current in various devices, and how it can be determined with the help of other factors.
· Students will study different circuits in which a number of resistors and cells are interconnected for which different calculations need to be done to obtain different values of current, resistance, etc., with the help of Class 12 Physics NCERT Exemplar solutions chapter 3
· NCERT Exemplar Class 12 Physics solutions chapter 3 also introduces different devices such as potentiometer, meter bridge and exhibits the methods, and formulas for understanding current, resistance, etc., through these devices.
Also read NCERT Solution subject wise
Must read NCERT Notes subject wise
Also Check NCERT Books and NCERT Syllabus here:
Yes, current electricity is one of the most crucial chapters that one needs to focus on for getting good marks in boards and entrance exams.
Our teachers have solved all questions from NCERT exemplar Class 12 Physics chapter 3 current electricity with complete steps and details.
One can make use of these solutions to understand the questions to the best and also understand how to solve questions in exams.
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Hello there! Thanks for reaching out to us at Careers360.
Ah, you're looking for CBSE quarterly question papers for mathematics, right? Those can be super helpful for exam prep.
Unfortunately, CBSE doesn't officially release quarterly papers - they mainly put out sample papers and previous years' board exam papers. But don't worry, there are still some good options to help you practice!
Have you checked out the CBSE sample papers on their official website? Those are usually pretty close to the actual exam format. You could also look into previous years' board exam papers - they're great for getting a feel for the types of questions that might come up.
If you're after more practice material, some textbook publishers release their own mock papers which can be useful too.
Let me know if you need any other tips for your math prep. Good luck with your studies!
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Hi,
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hello mahima,
If you have uploaded screenshot of your 12th board result taken from CBSE official website,there won,t be a problem with that.If the screenshot that you have uploaded is clear and legible. It should display your name, roll number, marks obtained, and any other relevant details in a readable forma.ALSO, the screenshot clearly show it is from the official CBSE results portal.
hope this helps.
Hello Akash,
If you are looking for important questions of class 12th then I would like to suggest you to go with previous year questions of that particular board. You can go with last 5-10 years of PYQs so and after going through all the questions you will have a clear idea about the type and level of questions that are being asked and it will help you to boost your class 12th board preparation.
You can get the Previous Year Questions (PYQs) on the official website of the respective board.
I hope this answer helps you. If you have more queries then feel free to share your questions with us we will be happy to assist you.
Thank you and wishing you all the best for your bright future.
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