Science (English Medium) Class 12 - CBSE Question Bank Solutions for Physics

Two-point charges q₁ and q₂ are kept at a distance of r₁₂ in air. Deduce the expression for the electrostatic potential energy of this system.

If an external electric field (E) is applied on the system, write the expression for the total energy of this system.

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Alloys usually have much (lower/higher) temperature coefficients of resistance than pure metals.

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The resistivity of the alloy manganin is nearly independent of/increases rapidly with increase of temperature.

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The resistivity of a typical insulator (e.g., amber) is greater than that of a metal by a factor of the order of (10²²/10²³).

Which of the following methods can be used to charge a metal sphere positively without touching it? Select the most appropriate.

According to Gauss’s law for magnetism ______.

Total internal reflection can take place only if light is travelling from ______.

Optical fibre communication uses the principle of ______.

Wavefront is ______.

When a beam of light is used to determine the position of an object, the maximum accuracy is achieved, if the light is ______.

In Photoelectric effect ______.

In the experimental set up for studying photoelectric effect, if keeping the frequency of the incident radiation and the accelerating potential fixed, the intensity of light is varied, then ______.

For a given frequency of light and a positive plate potential in the set up below, If the intensity of light is increased then ______.

In various experiments on photo electricity, the stopping potential for a given frequency of the incident radiation is ______.

The surface charge density of a thin charged disc of radius R is σ. The value of the electric field at the center of the disc is `sigma/(2∈_0)`. With respect to the field at the center, the electric field along the axis at a distance R from the center of the disc ______.