NEB Class 12 Science Physics Question Paper 2077

Why is the conductivity of an electrolyte very low as compared to a metal at room temperature?

What are the advantages of A.C. over D.C.?

Production of X-ray is the inverse phenomenon of photoelectric effect. Justify it.

What is the threshold of hearing? Define one bel.

Is polarization possible for longitudinal waves? Justify.

Why has an ammeter a very low resistance? How can you convert a galvanometer into an ammeter?

Explain the working of He-Ne laser.

What is Doppler effect? Find the change in frequency when an observer moves towards a stationary source and then moves away from the source.

Describe Michelson's method to measure the velocity of light.

The total length of the wire of a potentiometer is 10 m. A potential gradient of $0.0015\,\text{V/cm}$ is obtained when a steady current is passed through this wire. Calculate,

i) the distance of null point on connecting standard cell of $1.018\,\text{V}$.

ii) the unknown p.d. if the null point is obtained at a distance of $940\,\text{cm}$, and

iii) the maximum p.d. which can be measured by this instrument.

$_{28}\text{Ni}^{62}$ may be described as the most strongly bound nucleus because it has the highest B.E. per nucleon. Its neutral atomic mass is $61.928349\,\text{a.m.u.}$ Find its mass defect, its total binding energy and binding energy per nucleon.

Given, mass of neutron $= 1.008665\,\text{amu}$, mass of proton $= 1.007825\,\text{amu}$, $1\,\text{amu} = 931.5\,\text{MeV}$.

A source of sound produces a note of $512\,\text{Hz}$ in air at $17^{\circ}\text{C}$ with wavelength $66.5\,\text{cm}$. Find the ratio of molar heat capacities at constant pressure to constant volume at NTP. Densities of air and mercury at NTP are $1.293\,\text{kg/m}^3$ and $13600\,\text{kg/m}^3$ respectively.

Two coherent sources A and B of radio waves are $5\,\text{m}$ apart. Each source emits waves with wavelength $6\,\text{m}$. Consider points along the line between two sources, at what distances, if any, from A is the interference constructive?