HSC Science (Computer Science) 12th Standard Board Exam - Maharashtra State Board Question Bank Solutions

Draw a neat diagram of a full-wave rectifier and explain it’s working.

Using the energy conservation, derive the expressions for the minimum speeds at different locations along a vertical circular motion controlled by gravity. Is zero speed possible at the uppermost point? Under what condition/s?

Using energy conservation, along a vertical circular motion controlled by gravity, prove that the difference between the extreme tensions (or normal forces) depends only upon the weight of the objects.

Two charges of magnitudes −4Q and + 2Q are located at points (2a, 0) and (5a, 0) respectively. What is the electric flux due to these charges through a sphere of radius 4a with its centre at the origin?

Answer in brief.

The amplitude of a wave is represented by y = 0.2 sin 4π `["t"/0.08-"x"/0.8]` in SI units. Find (a) wavelength, (b) frequency, and (c) amplitude of the wave.

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]

If the effective current in a 50 cycle AC circuit is 5 A, what is the peak value of current? What is the current 1/600 after if was zero?

Using the values of work function given in the following table, tell which metal will require the highest frequency of incident radiation to generate photocurrent.

Typical values of work function for some common metals

It is observed in an experiment on the photoelectric effect that an increase in the intensity of the incident radiation does not change the maximum kinetic energy of the electrons. Where does the extra energy of the incident radiation go? Is it lost? State your answer with explanatory reasoning.

Photocurrent recorded in the microammeter in an experimental setup of the photoelectric effect vanishes when the retarding potential is more than 0.8 V if the wavelength of incident radiation is 4950 Å. If the source of incident radiation is changed, the stopping potential turns out to be 1.2 V. Find the work function of the cathode material and the wavelength of the second source.

The threshold wavelength of tungsten is 2.76 x 10^-5 cm.
(a) Explain why no photoelectrons are emitted when the wavelength is more than 2.76 x 10^-5 cm.
(b) What will be the maximum kinetic energy of electrons ejected in each of the following cases

(i) if ultraviolet radiation of wavelength λ = 1.80 × 10^-5 cm and
(ii) radiation of frequency 4 x 10¹⁵ Hz is made incident on the tungsten surface?

Radiation of wavelength 4500 Å is incident on a metal having work function 2.0 eV. Due to the presence of a magnetic field B, the most energetic photoelectrons emitted in a direction perpendicular to the field move along a circular path of radius 20 cm. What is the value of the magnetic field B?

Given the following data for incident wavelength and the stopping potential obtained from an experiment on the photoelectric effect, estimate the value of Planck's constant and the work function of the cathode material. What is the threshold frequency and corresponding wavelength? What is the most likely metal used for emitter?

Insect moves over the surface of water because of ______.

The water droplets are spherical in free fall due to ______ 

The surface tension of a liquid at critical temperature is ______ 

Define surface tension.

What will be the shape of the liquid meniscus for the obtuse angle of contact? 

Water rises to a height of 20 mm in a capillary tube. If the radius made 1/3^rd of its previous value, to what height will the water now rise in the tube?  

Two soap bubbles have a radius in the ratio of 2:3. Compare the works done in blowing these bubbles.