 # CBSE Class 12 Physics Solved Practice Paper (Set - 3)

Find CBSE Class 12 Physics Solved Practice Paper (Set - 3). Get the idea that what types of questions had been asked in the CBSE Class 12 Board Exam Papers.

Aug 19, 2015 09:48 IST

Find CBSE Class 12 Physics Solved Practice Paper (Set - 3). The Practice Paper only covers Unit I to IV. These questions not only helps the students to prepare for exams in a better manner, but also help them in understanding the depth with which a topic should be studied.

Few Sample Questions from the Question Paper are given below:

Q. Consider a metallic pipe with an ineer radius of 1 cm. If a cylindrical bar magnet of radius 0.8 cm is dropped through the pipe, it takes more time to come down than it takes for a similar unmagnetised cylindrical iron bar dropped through the metallic pipe. Explain.

Sol. When a cylindrical bar magnet is dropped through the metallic pipe, amount of flux linked with the pipe changes. Eddy currents are induced in the pipe, which oppose the free fall of bar magnet. The acceleration of bar magnet will be less than ‘g’, acceleration due to gravity. Therefore, it takes more time to come down the pipe.

When a similar unmagnetised cylindrical iron bar is dropped through the metallic pipe, there are no eddy currents as magnetic flux linked with the pipe does not change. Hence, there is no opposition to free fall of the iron bar under gravity, i.e., its downward acceleration = g. Hence, the iron bar takes lesser time to come down the pipe.

Q. Four point charges qA = 2 μC, qB = –5 μC, qC = 2 μC, and qD = –5 μC are located at the corners of a square ABCD of side 10 cm. What is the force on a charge of 1 μC placed at the centre of the square?

Sol. The charges of equal magnitude and same sign are at the corners of same diagonal. So they will exhibit equal and opposite forces at the charge situated in the centre, cancelling out each other. So the force is zero newton.

Q. Why should an ammeter have low resistance and high current carrying capacity?

Sol. An ammeter is used to measure current. It can measure the current of the circuit if connected in series of the circuit. The ammeter connected in series of the circuit can measure the current and will not disturb the current of the circuit if its resistance is low and current carrying capacity is high.

Q. What is the advantage of using thick metallic strips to join wires in a potentiometer?

Sol. In potentiometer the number of straight wires each of length 1 metre is held parallel on a horizontal wooden board and joined by thick metal strips in order to have long effective length of potentiometer wire which is required for accurate measurement. Since, the resistance of thick copper strips is very very small, can be ignored; while measuring the potentiometer length of the null point. The potentiometer length for null deflection can be noted down directly from the metre scale provided on the wire, which leads to accurate measurement.