Electron, Photon, Photoelectric Effect and X-Rays — Physics STD 12 Science — Question

An alternating current having peak value 14A is used to heat a metal wire. To produce the same heating effect, a constant current i can be used where i is:

Additivity of the electric charges means that the total charge of a system is the _____ of all individual charges in the system.

A current of 16 ampere flows through molten NaCl for 10 minute. The amount of metallic sodium that appears at the negative electrode would be(a) 0.23 gm(b) 1.15 gm(c) 2.3 gm(d) 11.5 gm

When a dielectric is introduced between the plates of a condenser, the capacity of condenser:

The distance between the plates of a parallel plate condenser is 4mm and potential difference is 60 volts. If the distance between the plates is increased to 12mm, then(a) The potential difference of the condenser will become 180 volts(b) The P.D. will become 20 volts(c) The P.D. will remain unchanged(d) The charge on condenser will reduce to one third

A plano-convex lens of refractive index 1.5 and radius of curvature 30 cm is silvered at the curved surface. Now this lens has been used to form the image of an object. At what distance from this lens an object be placed in order to have a real image of the size of the object(a) 20 cm(b) 30 cm(c) 60 cm(d) 80 cm

Which of the following series of hydrogen spectrum is in visible range?

The half life period of a radioactive element X is same as the mean life time of another radioactive element Y. Initially both of them have the same number of atoms. Then(a) X and Y have the same decay rate initially(b) X and Y decay at the same rate always(c) Y will decay at a faster rate than X(d) X will decay at a faster rate than Y