Question

11. Four identical 1 mF capacitors are connected together electrically. What is the least possible capacitance of the combination? a. I mF b. 1/8 m c. 4 mF d. 1/4 mF 12. Q. has 50 electric field lines radiating outward and Q, has 100 field lines converging inward. What is the ratio Q./0,? a. 2 b. -2 'c. 1/2 d. -1/2 16. A uniform 45-T magnetic field passes through the plane of a wire loop 0.10 min area. What flux passes through the loop when the direction of the 4.5-T field is at a 30° angle to the normal of the loop plane? a. 5.0 T-m2 b. 0.39 T-m C. 0.52 T-m? d. 0.225 T- 17. After light from a source passes through two slits, a first order bright spot is seen on the wall at point P. Which distance is equal to the wavelength of the light? P D B ...... 13. A silicon monoxide (n = 1.45) film of 100 nm thickness is used to coat a glass camera lens ( 1.56). What wavelength of light in the visible region (390 to 710 nm) will be most efficiently transmitted by this system? (1 nm - 10 m) a. 400 nm b. 492 nm c. 624 nm d. 580 nm a the extra distance one beam must travel b. the distance between beams as they leave the slit C. the distance between slits d the distance of point from the central point of the interference pattern 18. The unit of electric current, the ampere, is equivalent to which of the following? a V/Q2 b. V.Q c. Vis 14. The force on a charged particle created by its motion in a magnetic field is maximum at what angle between the particle velocity and field? a. 45° b. 180° c. zero d. 90° 15. What is the minimum thickness of a glycerin film (n=1.47) on which light of wavelength 600 nm shines that results in constructive interference of the reflected light? Assume the film is surrounded front and back by air. a. 102 nm b. 204 nm c. 75 nm d. 150 nm 19. Household circuits are wired in a. parallel b. both series and parallel c. neither series nor parallel d. series 20. Which of the following best describes the image from a plane mirror? a. real and magnification equal to one b. real and magnification less than one c. virtual and magnification equal to one d virtual and magnification greater than one

Answer 1

11.

The equivalent capacitance for capacitors connected in series is given by

                                                      

                                     or,          

The equivalent capacitance for the capacitors connected in parallel is given by

                                                    

So, if we connect four 1 mF capacitor in parallel then the equivalent capacitance will be

                                                     

So, if we connect four 1 mF capacitor in series then the equivalent capacitance will be

                                                     

12.

The electric field lines show the strength of the field in the region.

It is clear that the strength of the electric field due to the charge Q₂ is twice of that of the field due to the charge Q₁.

The electric field due to the charge Q₁ at a distance 'r' is given by

                                              

So, the ratio of both the charges will be

                                              

But both the charges are of opposite nature. So,

                                                

Answer 2

In case of series the total capicitance will be 1/4mf. While in case of parallel combination the total capicitance of a capacitor will be 4mF.