Electric Charges and Fields — Physics STD 12 Science — Question

If the current is doubled, the deflection is also doubled in:

The current in a simple series circuit is 5.0 amp. When an additional resistance of 2.0 ohms is inserted, the current drops to 4.0 amp. The original resistance of the circuit in ohms was(a) 1.25(b) 8(c) 10       (d) 20

In series combination of capacitors the effective capacitance:

In an X-ray tube electrons bombarding the target produce X-rays of minimum wavelength 1 Å. What must be the energy of bombarding electrons (a) 13375 eV(b) 12375 eV(c) 14375 eV(d) 15375 eV

We are able to obtain fairly large currents in a conductor because(a) The electron drift speed is usually very large(b) The number density of free electrons is very high and this can compensate for the low values of the electron drift speed and the very small magnitude of the electron charge(c) The number density of free electrons as well as the electron drift speeds are very large and these compensate for the very small magnitude of the electron charge(d) The very small magnitude of the electron charge has to be divided by the still smaller product of the number density and drift speed to get the electric current

The image which can be obtained on a screen is called:

The human eye has a lens which has a(a) Soft portion at its centre(b) Hard surface(c) Varying refractive index(d) Constant refractive index

Large transformers, when used for some time, become hot and are cooled by circulating oil. The heating of transformer is due to(a) Heating effect of current alone(b) Hysteresis loss alone(c) Both the hysteresis loss and heating effect of current(d) None of the above

It is essential to consider light as a stream of photons to explain: