Electrostatics — Physics STD 12 Science — Question

Four resistances 10 W, 5 W, 7 W and 3 W are connected so that they form the sides of a rectangle AB, BC, CD and DA respectively.  Another resistance of 10 W is connected across the diagonal AC. The equivalent resistance between A and B is

(a) 2 W

(b) 5 W

(c) 7 W

(d) 10 W

Which one of the following statements about uranium is correct

(a)  is fissionable by thermal neutrons

(b) Fast neutrons trigger the fission process in

(c)  breaks up into fragments when bombarded by slow neutrons

(d)  is an unstable isotope and undergoes spontaneous fission

A cell is connected between two points of a uniformly thick circular conductor. The magnetic field at the centre of the loop will be (Here  and  are the currents flowing in the two parts of the circular conductor of radius ‘a’ and  has the usual meaning)

(a) Zero

(b)  (

(c) (

(d) (

Which of the following is/ are true for "magnetic lines of force around a bar magnet"?

Two beams of light having intensities I and 4I interfere to produce a fringe pattern on a screen. The phase difference between the beams is  at point A and p at point B. Then the difference between the resultant intensities at A and B is

(a) 2I

(b) 4I

(c) 5I

(d) 7I

A combination of two thin lenses of the same material with focal lengths  and , arranged on a common axis minimizes chromatic aberration, if the distance between them is

(a)

(b)

(c) (

(d)

The number of turns in the primary coil of a transformer is 200 and the number of turns in the secondary coil is 10. If 240 volt AC is applied to the primary, the output from the secondary will be

(a) 48 V

(b) 24 V

(c) 12 V

(d) 6 V

According to Einstein's interpretation of the photoelectric effect, the maximum K.E. of photoelectrons depends on ( h -W) where is the frequency of incident radiation and W is the work function. For three different metals graph plotted between maximum K/E. and the frequency of incident radiations. The three graphs obtained: 

The idea of parmanu was given by:

Mark the correct options:

1. Gauss's law is valid only for symmetrical charge distributions.
2. Gauss's law is valid only for charges placed in vacuum.
3. The electric field calculated by Gauss's law is the field due to the charges inside the Gaussian surface.
4. The flux of the electric field through a closed surface due to all the charges is equal to the flux due to the charges enclosed by the surface.