Current Electricity — Physics STD 12 Science — Question

What are isotopes? Explain with an example how the average mass can be obtained from the relative proportions of different isotopes of the same element.

A steel wire of mass 4.0g and length 80cm is fixed at the two ends. The tension in the wire is 50N. Find the frequency and wavelength of the fourth harmonic of the fundamental.

The drift current in a reverse-biased p-n junction increases in magnitude if the temperatu,re of the junction is increased. Explain this on the basis of creation of hole-electron pairs.

A long, straight wire of radius r carries a current i and is placed horizontally in a uniform magnetic field B pointing vertically upward. The current is uniformly distributed over its cross-section.

1. At what points will the resultant magnetic field have maximum magnitude? What will be the maximum magnitude?
2. What will be the minimum magnitude of the resultant magnetic field?

A uranium reactor develops thermal energy at a rate of 300MW. Calculate the amount of ²³⁵U being consumed every second. Average released per fission is 200MeV.

A charge Q is distributed uniformly over a metallic sphere of radius R. Obtain the expressions for the electric field (E) and electric potential (V) at a point 0 < x < R.
Show on a plot the variation of E and V with x for 0 < x < 2R.

An average emf of 20V is induced in an inductor when the current in it is changed from 2.5A in one direction to the same value in the opposite direction in 0.1s. Find the self-inductance of the inductor.

Obtain the formula of electric current for an AC circuit having only capacitor.

A magnifying glass is a converging lens placed close to the eye. A farsighted person uses spectacles having converging lenses. Compare the functions of a converging lens used as a magnifying glass and as spectacles.

Red light however bright it is, cannot produce the emission of electrons from a clean zinc surface, but even weak ultraviolet radiation can do so; why?