NEB Class 12 Science Physics (Technical Stream) Question Paper 2082

The moment of Linear momentum is called

A liquid does not wet the surface of a solid if the angle of contact is

In a thermodynamic process, if the volume remains constant, then the process is known as

A system suffers an increase in internal energy of 80 Joules and at the same time 50 Joules of work is done on the system. What is the value of heat supplied?

The reciprocal of wavelength is called

The distance between any two consecutive nodes in terms of wavelength ($\\lambda$) in a stationary wave is

For a diamagnetic material, which of the following statement is correct for the magnetic susceptibility ($\\chi$)?

Kirchhoff's voltage law is based on the principle of conservation of

Which of the following graphs represents correctly the variation of photoelectric current (Ip) with the intensity (I) of the radiation.

(A)

(B)

(C)

(D)

If K.E. of a particle is increased by four times then the de-Broglie wavelength becomes

During the reverse biasing of a P-N Junction diode, thickness of depletion Layer

Define moment of inertia. Write any two factors on which it depend.

Obtain an expression for the moment of inertia of a thin uniform rod about an axis passing through its centre and perpendicular to its length.

State the principle of conservation of angular momentum.

Define surface tension.

Show that surface tension of liquid is numerically equal to the surface energy.

Define capillarity with two suitable examples.

What correction was made by Laplace on Newton's formula? Obtain the corrected formula.

At what temperature the speed of sound is increased by 50% to that at 27^\\circ\\text{C}?

Define harmonics.

Describe the various modes of vibration of air column in an open organ pipe.

What is end correction of an organ pipe?

What is meant by diffraction of light?

Write the necessary condition for diffraction of light.

Interference occurs due to the superposition of two waves produced by the coherent sources.

i) Define coherent sources. [1]

ii) Write the required condition for constructive and destructive interference. [2]

a) State the principle of potentiometer. [1]

b) Why do we prefer potentiometer to measure emf of a cell rather than a voltmeter? Justify. [2]

c) State two Kirchhoff's laws of electrical circuit. [2]

Or

a) State and explain Biot-Savart's law. [2]

b) Obtain an expression for magnetic field intensity at the centre of a current carrying circular coil using Biot-Savart's law. [3]

How can a galvanometer be converted into an ammeter? Explain.

Why is an ammeter connected in series in a circuit? Justify.

a) State and explain Einstein photo electric equation. Also, define threshold frequency. [3]

b) If 5ev photon strikes on a surface of a metal of work function 1.8ev, calculate the maximum speed of the emitted electron. [2] ($h = 6.62\\times10^{-34}\\,\\text{Js}$), [Mass of an electron ($m$) = $9.1\\times10^{-31}\\,\\text{kg}$], [Charge on an electron ($e$) = $1.6\\times10^{-19}\\,\\text{C}$]

Or

a) Define rectifier. [1]

b) Explain with a neat diagram of full wave rectifier using two semi-conductor diodes. [3]

c) Plot input and output waveforms of full wave rectifier. [1]

Define simple harmonic motion.

A simple harmonic motion is given as $Y = a\\sin(wt - kx)$, where symbols have their usual meanings. Find its acceleration.

Show that the oscillation of mass suspended from a helical spring is simple harmonic motion.

A body of mass 200gm is executing SHM with amplitude of 20mm. The maximum force which acts upon it is 0.8N. Calculate the maximum velocity of the body.

Define r.m.s value of an ac.

How rms value of an ac is related to the peak value?

Show that current through a pure inductor Lags behind voltage by a phase angle $\\dfrac{\\pi}{2}$. Also draw its phasor diagram.

A series LCR circuit is shown in figure below.

$L = 30\\,\\text{mH}$, $C = 10\\,\\mu\\text{F}$, $R = 25\\,\\Omega$, $E = 250\\,\\text{V}$, $f = 50\\,\\text{Hz}$.

Calculate the impedance and current in the circuit.

a) Define cross field. [1]

b) Show that the motion of an electron in a magnetic field is circular. Also, determine its time period. [3]

c) An electron and proton are projected with the same speed in a uniform magnetic field normally. Compare the radius of their circular paths. [2]

d) Calculate the radius of a water drop which would just remains suspended in a electric field of $3\\times10^4\\,\\text{V/m}$ and charged with one electron. [2]

Or

a) Define ionization potential. [1]

b) Which spectral series of hydrogen atom lie within visible region? Calculate the longest wave length of that series. ($R = 1.097\\times10^{-7}\\,\\text{m}^{-1}$) [3]

c) How do you control quality of X-rays? Explain. [2]

d) Calculate the de-Broglie wave length of X-rays having K.E of 200ev. (Mass of electron = $9.1\\times10^{-31}\\,\\text{kg}$) [2]