Nucleus — Physics STD 12 Science — Question

In a material medium, when a positron meets an electron both the particles annihilate leading to the emission of two gamma ray photons. This process forms the basis of an important diagnostic procedure called

(a) MRI

(b) PET

(c) CAT

(d) SPECT

The intensity of the electric field required to keep a water drop of radius  just suspended in air when charged with one electron is approximately (g = 10 newton/kg e =  1.6

(a) 260 volt/cm	(b) 260 newton/coulomb
(c) 130 volt/cm	(d) 130 newton/coulomb

The capacity of a condenser is 4   farad and its potential is 100 valts. The energy released on discharging it fully will be

(a) 0.02 Joule

(b) 0.04 Joule

(c) 0.025 Joule

(d) 0.05 Joule

Assertion  :   An aircraft flies along the meridian, the potential at the ends of its wings will be the same.

Reason     : Whenever there is change in the magnetic flux e.m.f. induces.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Number of electrons in one coulomb of charge will be

(a) 5.46

(b)  6.25

(c) 1.6

(d) 9

The current sensitivity of a moving coil galvanometer can be increased by

(a) Increasing the magnetic field of the permanent magnet

(b) Increasing the area of the deflecting coil

(c) Increasing the number of turns in the coil

(d) a, b, c

In case of the electromagnetic waves the angle between the electric and magnetic field vectors is.

Two capacitors of 3pF and 6pF are connected in series and a potential difference of 5000 V is applied across the combination. They are then disconnected and reconnected in parallel. The potential between the plates is

(a) 2250 V

(b) 2222 V

(c) 2.25

(d) 1.1

In an insulator, the forbidden energy gap between the valence band and conduction band is of the order of      

(a) 1 MeV

(b) 0.1 MeV

(c) 1eV

(d) 5 eV

If a proton is projected in a direction perpendicular to a uniform magnetic field with velocity v and an electron is projected along the lines of force, what will happen to proton and electron

(a) The electron will travel along a circle with constant speed and the proton will move along a straight line

(b) Proton will move in a circle with constant speed and there will be no effect on the motion of electron

(c) There will not be any effect on the motion of electron and proton

(d) The electron and proton both will follow the path of a parabola