Physics Shaalaa.com Model Set 1 2020-2021 HSC Science (General) 12th Standard Board Exam Question Paper Solution

Which of the following is correct, when the energy is transferred to a system from its environment?

System gains energy

System loses energy

System releases energy

the system does not exchange energy

For work done to be reversible, the process should be ______ 

cyclic

isobaric

isochoric

adiabatic

A particle is performing simple harmonic motion with amplitude A and angular velocity ω. The ratio of maximum velocity to maximum acceleration is ______.

ω

1/ω

ω²

A/ω

In the law of tension, the fundamental frequency of the vibrating string is, ______   

inversely proportional to the square root of tension

directly proportional to the square of tension

directly proportional to the square root of tension

inversely proportional to the density 

The integral multiple of fundamental frequencies are ______ 

beats

resonance

overtones

harmonics

A LED emits visible white light when its ______  

junction is reversed-biased.

depletion layer widens.

holes and electrons recombine.

junction becomes hot.

Insect moves over the surface of water because of ______.

Elasticity

Surface tension

Friction

Viscosity

Two capillary tubes of radii 0.6 cm and 0.3 cm are dipped in the same liquid. The ratio of heights through which the liquid will rise in the tubes is ______.

2 : 1

1 : 2

4 : 1

1 : 4

Light of wavelength 5000 A.U. falls on a plane reflecting surface. The frequency of reflected light is ______ 

6 × 10¹⁴Hz 

5 × 10¹⁴Hz

2 × 10¹⁴Hz

1.666 × 10¹⁴Hz 

You are given a number of capacitors labelled as 8μF - 250V. Find the number of capacitors needed to get an arrangement equivalent to 16μF - 1000V. 

4

16

32

64

What are cohesive forces?

Under which condition laws of Boyle, Charles, and Gay-Lussac are valid?

When two objects are said to be in thermal equilibrium?

A simple pendulum moves from one end to the other in ¼ second. What is its frequency?

What is the basis of Kirchhoff’s current law and voltage law?

What does the ratio of magnetization to magnetic intensity indicate? 

A square metal plate of area 100 cm² moves parallel to another plate with a velocity of 10 cm/s, both plates immersed in water. If the viscous force is 200 dyne and the viscosity of water is 0.01 poise, what is the distance between them?   

What do you mean by dielectric polarization?

A flywheel is revolving with a constant angular velocity. A chip of its rim breaks and flies away. What will be the effect on its angular velocity?

Draw a p-V diagram of the reversible process. 

Draw a p-V diagram showing negative work with varying pressure. 

Distinguish between an overtone and harmonic. 

What are stationary waves? Why are they called stationary waves? 

Draw a neat labelled diagram of a schematic of the experimental setup for the photoelectric effect. 

State any two advantages and disadvantages of a photodiode. 

The moment of inertia of a body about a given axis is 1.2 kgm². initially, the body is at rest. For what duration on the angular acceleration of 25 radian/sec² must be applied about that axis in order to produce rotational kinetic energy of 1500 joule?  

1000 calories of radiant heat are incident on a body. If the body absorbs 400 calories of heat, find the coefficient of emission of the body. 

Four resistances 6Ω, 6Ω, 6Ω and 18Ω form a Wheatstone bridge. Find the resistance which connected across the 18Ω resistance will balance the network.

The magnetic flux through a loop varies according to the relation Φ = 8t² + 6t + 2, Φ is in milliweber and t is in second. What is the magnitude of the induced emf in the loop at t = 2 seconds?  

Define current amplification factor α_DC and β_DC Obtain the relation between them. 

Derive an expression for the kinetic energy of a rotating body with uniform angular velocity. 

Explain the phenomena of surface tension on the basis of molecular theory.

Obtain an expression for the resultant amplitude of, the composition of two S.H.M.’s having the same period along the same path.  

Explain the reflection of light at a plane surface with the help of a neat ray diagram. 

Describe Young’s double-slit experiment with a neat diagram showing points of maximum and minimum intensity. 

Explain the construction and working of the Moving coil Galvanometer.  

Explain the term inductive reactance. State its unit and dimensions.

An alternating emf of 230V, 50Hz is connected across a pure ohmic resistance of 50Ω. Find (1) the current (2) equations for instantaneous values of current and voltage.

The work function of a surface is 3.1 eV. A photon of frequency 1 × 10¹⁵ Hz. Is an incident on it. Calculate the incident wavelength is photoelectric emission occurs or not.   

The primary of a transformer has 40 turns and works on 100 V and 100 W. Find a number of turns in the secondary to step up the voltage to 400 V. Also calculate the current in the secondary and primary.

A circular loop of radius 9.7 cm carries a current 2.3 A. Obtain the magnitude of the magnetic field
(a) at the centre of the loop
(b) at a distance of 9.7 cm from the centre of the loop but on the axis.

A cell of e.m.f 1.5V and negligible internal resistance is connected in series with a potential meter of length 10 m and the total resistance of 20 Ω. What resistance should be introduced in the resistance box such that the potential drop across the potentiometer is one microvolt per cm of the wire?  

Explain the spectral distribution of blackbody radiation.

State the postulates of Bohr’s atomic model. Hence show the energy of electrons varies inversely to the square of the principal quantum number. 

Draw a neat labelled diagram showing energy levels and transition between them for the hydrogen atoms. 

An electron in an atom is revolving around the nucleus in a circular orbit of a radius of 5.3 x 10^-11 m, with a speed of 2 x 10⁶ m/s. Find the resultant orbital magnetic moment and angular momentum of the electron. [e = 1.6 x 10^-19 C, m_e= 9.1 x 10^-31 kg]

Define Magnetization.

State SI unit of Magnetization.

State dimensions of Magnetization.

Derive the relation between magnetic field intensity(H) and magnetization(M) for a magnetic material placed in a magnetic field. 

Two capacitors each of capacity 2 μF are connected in parallel. This system is connected in series with the third capacitor of 12μF capacity. Find the equivalent capacity of the system.  

Using Ampere's law, obtain an expression for the magnetic induction near a current-carrying straight infinitely long wire. 

Two spheres A and B of radius a and b respectively are at the same potential. Find the ratio of the surface charge densities of A and B.