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

A 1000 MW fission reactor consumes half of its fuel in 5.00 y. How much `""_92^235"U"` did it contain initially? Assume that the reactor operates 80% of the time, that all the energy generated arises from the fission of `""92^235"U"` and that this nuclide is consumed only by the fission process.

Calculate and compare the energy released by a) fusion of 1.0 kg of hydrogen deep within Sun and b) the fission of 1.0 kg of ²³⁵U in a fission reactor.

Suppose India had a target of producing by 2020 AD, 200,000 MW of electric power, ten percent of which was to be obtained from nuclear power plants. Suppose we are given that, on an average, the efficiency of utilization (i.e. conversion to electric energy) of thermal energy produced in a reactor was 25%. How much amount of fissionable uranium would our country need per year by 2020? Take the heat energy per fission of ²³⁵U to be about 200MeV.

When a forward bias is applied to a p-n junction, it ______.

In the following diagram 'S' is a semiconductor. Would you increase or decrease the value of R to keep the reading of the ammeter A constant when S is heated? Give reason for your answer.

Draw its I – V characteristics of photodiode

Find the wavelength of the electron orbiting in the first excited state in hydrogen atom.

In the following diagram, is the junction diode forward biased or reverse biased ?

A pair of adjacent coils has a mutual inductance of 1.5 H. If the current in one coil changes from 0 to 20 A in 0.5 s, what is the change of flux linkage with the other coil?

Consider two concentric circular coils, one of radius r₁ and the other of radius r₂ (r₁ < r₂) placed coaxially with centers coinciding with each other. Obtain the expression for the mutual inductance of the arrangement.

Four point charges Q, q, Q and q are placed at the corners of a square of side 'a' as shown in the figure.

Find the

1) resultant electric force on a charge Q, and

2) potential energy of this system.

Find out the amount of the work done to separate the charges at infinite distance.

A point charge Q is placed at point 'O' as shown in the figure. Is the potential at point A, i.e. V_A, greater, smaller or equal to potential, V_B, at point B, when Q is (i) positive, and (ii) negative charge?

The figure shows three infinitely long straight parallel current carrying conductors. Find the

1. magnitude and direction of the net magnetic field at point A lying on conductor 1,
2. magnetic force on conductor 2.

A point charge Q is placed at point O as shown in the figure. The potential difference V_A – V_B positive. Is the charge Q negative or positive?

Show variation of resistivity of Si with temperature in a graph ?

Plot a graph showing variation of current versus voltage for the material GaAs ?

Figure shows the field lines due to a positive point charge. Give the sign of potential energy difference of a small negative charge between the points Q and P.

Plot a graph showing the variation of photoelectric current with collector plate potential at a given frequency but for two different intensities I₁ and I₂, where I₂ > I₁.

Give two points to distinguish between a paramagnetic and a diamagnetic substance ?