# CBSE Class 12 Physics Solved Practice Paper for 2018 Board Exam: Set I

Sep 10, 2018 12:11 IST
CBSE Class 12 Physics Solved Paper

CBSE Solved Paper for Class 12 Physics board exam is available here. During last few months before exams, practice is more important than studying anything new. In order to help the students, here we have provided a completely solved paper. Besides important questions, this paper also contains some out of the box conceptual questions and important numerical problems.

In this paper, you will find 26 questions divided into 5 sections (Section A, B, C, D and E). More detail about types of questions is given below:

CBSE Class 12 Physics Sample Paper 2018 (with Hints and Marking Scheme)

Few solved questions from the paper are given below:

Question: What is the shunt?

Solution:

A shunt is a low resistance wire connected in parallel to the galvanometer. It protects the device from strong current.

Question: A 100m long antenna is mounted on a 500m tall building. The complex can become a transmission tower for waves with λ.

Solution:

We know that, wavelength of the wave which can be transmitted by

λ ≈ 4l = 4 × 100 = 400 m

Question:

Force of attraction between two point charges placed at a distance r is F. Calculate the distance apart should they kept in the same medium so that the force between them is F/3?

Solution:

We know that,

F r2

According to the question,

New distance = r √3.

Question: A glass lens of refractive index 1.45 disappears when immersed in a liquid. What is the value of refractive index of the liquid?

Solution:

For disappearance of glass lens in liquid, refractive index of liquid = refractive index of lens = 1.45.

Question: Name the phenomena which establish wave nature of light.

Solution:

Diffraction, polarization of light and interference.

Question: What percentage of a given mass of a radioactive substance will be left undecayed after four half lives?

Solution:

If No is the initial quantity of radioactive element, then the quantity N of the element left after n half-live is given by: N = No(1/2)n.

The amount of substance left after 4 half lives can be given as:

N = No(1/2)4 = No/16 or 6.25% of initial value.

Question: What percentage of a given mass of a radioactive substance will be left undecayed after four half lives?

Solution:

If No is the initial quantity of radioactive element, then the quantity N of the element left after n half-live is given by: N = No(1/2)n.

The amount of substance left after 4 half lives can be given as:

N = No(1/2)4 = No/16 or 6.25% of initial value.

Question: Write two ways by which the range of transmission can be increased?

Solution:

Range of transmission of T.V. signal can be increase

• By increasing the power of transmitting signal from TV station

• By increasing the heights of transmitting and receiving antenna.

Question: Write two important limitations of Rutherford nuclear model of the atom.

Solution:

Important limitations of Rutherford nuclear model of the atom are:

1. It could not explain why atoms emit light of only discrete wavelengths. for example could a simple atom like hydrogen, consisting of a single electron and a single proton, emit a complex spectrum of specific wavelengths.

2. He did not say anything about the arrangement of an electron in an atom.

3. According to Maxwell, accelerated charged particles emit electromagnetic radiations and hence an electron revolving around the nucleus should emit electromagnetic radiation. This radiation would carry energy from the motion of the electron which would come at the cost of shrinking of orbits. Ultimately the electrons would collapse in the nucleus. This was a major limitation regarding the stability of an atom.

Other questions and solutions are available in the PDF.