# Top Ten important exam question from physics

In CBSE and State board and NEB Exam, A lots of questions asked some of them are too much hard that it became difficult for the students to get a pass also so today we are going to discuss those questions and their answers too. which help the students to get pass marks and those students who already are good at study this will help them to get better marks than they secure.

If you want some other subjects notes then check it out here  “Chemistry”  “Biology

Today we are going to talk about The top ten most exams asked questions.

Top Ten exam Questions for physics CBSE, the state board, and NEB ( national exam board)

1. State and explain Faraday’s law of electrolysis and establish a relation between chemical equivalent and an electrochemical equivalent of the material.

Ans. The amount of charge required to liberate one mole of a monovalent substance in electrolysis is called Faraday constant(F)

Let N atoms be liberated in an electrolysis when q charge is passed. If v be the valency of the substance, then total charge liberated can be written as Nve, where e is an electronic charge. Using principle of conservation of charge, we can write,

Charge supplied= Charge liberated q= NVe

for one mole of monovalent substance this relation q= Nve

F=NaE Where F is faraday constant Na is Avogadro constant. Thus, Farady constant may be defined as the amount if charge present in one mole of electron putting Na=6.022*10^23 mol-1 and e=1.6*10^-19C, we get F=96500C mol-1

Again, consider a certain amount of charge passed through an electrolyte so that one mole of an element having atomic mass A and valency v is liberated. In such case, amount of mass liberated will be equal to its atomic mass and amount of charge liberated is NaVe. Now, Faraday’s First law m=Zq in such case becomes.

2. What do you mean by Biasing a transistor?

Ans. In a transistor, a thin layer of one type of extrinsic semiconductor is sandwiched between two thick layers of another type of extrinsic semiconductor. This thin layer of a transistor is called base which is sandwitched by emitter and collector. The junction between emitter and base junction, while the junction between collector and base is called a collector-base junction, is reversed biased. This is called biasing-Whereas its collector-base junction is reversed biased. this is called biasing a transistor. Actually, application of dc voltage across the transistor is biasing.

3. Point out the importance of De-Broglie wave.

Ans. Importance of De-Broglie wave is as follows.

(i)The idea of De Broglie wave assigns a wavelength to each moving particle and reveals the dual nature of matter like the dual nature of radiations.

(ii)Bohr could not reason for the quantization when he proposed quantized electron orbits. But the idea of De Broglie wave, the electron wave is a standing wave and hence each orbit should contain an integer multiple of the wavelength i.e the circumference of each circular orbit, (2pieRn)=Na, where n=1,2,3.

physics importamt question

4.It is easier to start a car engine on a warm day than on a chilly day,why?

Ans. In a warm day, the temperature is high. At high temperature, more electrolyte in a battery dissociates into icons. As a result, the internal resistance of the battery decreases and hence, more current flows from the battery. Hence, in the case the internal resistance is very large, the current in the short circuit is limited by the internal resistance and save the source from damaging.

5. What do you understand by Laplace’s correction? Discuss the effect of temperature and pressure on velocity of sound.

6. What is photo Electric effect? Discuss Einstein’s Photoelectric equation. Does the work function of a metal depending on the intensity of light?

Ans. The phenomenon of emission of electrons from a metal surface, when illuminated by radiation of suitable wavelength, is called photoelectric effect. These electrons emitted are called photoelectrons.

To explain photoelectric was the result of the interaction of a single photon with an electron in which the photon is completely absorbed by the electron. thus, when a photon of radiation of frequency v is incident on a metal, a party of energy acquired by an electron is used to just pull out the electron from the surface of a metal, called work function (phie) and the rest of it appears as the maximum kinetic energy of the emitted electron.

:- Energy of a photon= work function of a metal + K.E of the emitted electron

Where m is the mass of an electron and Vmax is its maximum velocity. This relation is known as Einstein’s photoelectric equation. If Vo is the threshold frequency which just ejects an electron from the metal with zero velocity. then,

physics important questions

This equation is another from Einstein’s photoelectric equation.

The work function of a metal doesn’t depend on the intensity of height but depend on the frequency of the radiation and nature of the metal.

8. How can the intensity of X-ray be controlled in a cooling tube?

Ans. The intensity of x-ray depends upon the number of electrons striking the target per second. Also, the number of the electron emitted by the filament is proportional to its temperature which can be adjusted by the varying current in the filament circuit. Hence the intensity of X-ray can be controlled by controlling the filament current.

9. What is watless current?

Ans. The current in an A.C  circuit is watless if the average power consumed in the circuit is zero. this is possible only when the phase difference between the current and the voltage is Pie/2. it can be obtained by using an inductor or a capacitor in the circuit. that is, if a circuit doesn’t have any resistance, no power is consumed in the circuit.

10. State Huygen’s principle.

Ans.  (i) Each point on the primary (given) wavefront acts as a source of secondary wavelets, sending out a disturbance in all directions in a similar manner as the original source of light does.

(ii) The new position of the wavefront at any instant is given by the forward envelope of the secondary wavelets at that instant.

Corpuscular theory of light explains interference, diffraction, and polarization of light. These phenomena can be explained by the wave theory of light which is based on a geometrical construction called Huyen’s principal

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