HSC Science (General) १२ वीं कक्षा - Maharashtra State Board Important Questions for Physics

An alternating voltage is given by e = 8sin628.4t. Find

1. peak value of e.m.f.
2. frequency or e.m.f.
3. instantaneous value of e.m.f. at time t = 10. ms

Draw a neat labelled diagram for the construction of 'cyclotron'

The combined resistance of a galvanometer of resistance 500Ω and its shunt is 21Ω. Calculate the value of shunt.

A rectangular coil of a moving coil galvanometer contains 50 turns each having area 12 cm2 . It is suspended in radial magnetic field 0.025 Wb/m² by a fibre of twist constant 15 x10^-10 Nm/degree. Calculate the sensitivity of the moving coil galvanometer.

Show that the current flowing through a moving coil galvanometer is directly proportional to the angle of deflection of coil.

In a cyclotron, magnetic field of 3·5Wb/m2 is used to accelerate protons. What should be the time interval in which the electric field between the Dees be reversed?
(Mass of proton = 1· 67 x 10^-27Kg, Charge on proton =1·6x10^-19c).

A circular coil of 250 turns and diameter 18 cm carries a current of 12A. What is the magnitude of magnetic moment associated with the coil?

Draw a neat labelled diagram for Davisson and Germer experiment, for diffraction of electron wave.

An ideal voltmeter has _______.

(A) low resistance

(b) high resistance

(C) infinite resistance

(D) zero resistance

If a watch-glass containing a small quantity of water is placed on two dissimilar magnetic poles, then water ______.

Explain how moving coil galvanometer is converted into a voltmeter. Derive the necessary formula.

A rectangular coil of a moving coil galvanometer contains 100 turns, each having area
15 cm². It is suspended in the radial magnetic field 0.03 T. The twist constant of suspension
fibre is 15 x 10^-10 N-m/degree. Calculate the sensitivity of the moving coil galvanometer.

The fraction of the total current passing through the galvanometer is ............ .

a) `S/(S+G)`

b) `G/(S+G)`

c) `(S+G)/G`

d) `(S+G)/S`

A moving coil galvanometer has a resistance of 25Ω and gives a full scale deflection for a current of 10mA. How will you convert it into a voltmeter having range 0 - 100 V?

A galvanometer has a resistance of 16Ω. It shows full scale deflection, when a current of 20 mA is passed through it. The only shunt resistance available is 0.06  which is not appropriate to convert a galvanometer into an ammeter. How much resistance should be connected in series with the coil of galvanometer, so that the range of ammeter is 8 A?

Explain Ampere’s circuital law.

A cyclotron is used to accelerate protons to a kinetic energy of 5 MeV. If the strength of magnetic field in the cyclotron is 2T, find the radius and the frequency needed for the applied alternating voltage of the cyclotron. (Given : Velocity of proton= `3xx10^7 m//s`)

A photocell is used to automatically switch on the street lights in the evening when the sunlight is low in intensity. Thus it has to work with visible light. The material of the cathode of the photocell is ______.

What is the photoelectric effect?

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?