Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

The ______, a property of materials C, Si, and Ge depends upon the energy gap between their conduction and valence bands.

Two cells of 1.25 V and 0.75 V are connected in series with anode of one connected to cathode of the other. The effective voltage will be ______.

The magnetic field lines ______.

If we have two coherent sources S₁ and S₂ vibrating in phase, then for an arbitrary point P constructive interference is observed whenever the path difference is ______.

A long, hollow conducting cylinder is kept coaxially inside another long, hollow conducting cylinder of larger radius. Both the cylinders are initially electrically neutral ______.

Consider a current carrying wire (current I) in the shape of a circle.

Assertion: Bending a wire does not effect electrical resistance.
Reason: Resistance of wire is proportional to resistivity of material.

The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then ______.

Two spherical conductors each of capacity C are charged to potential V and -V. These are then connected by means of a fine wire. The loss of energy is ______.

A constant voltage is applied between the two ends of a uniform metallic wire, heat ‘H’ is developed in it. If another wire of the same material, double the radius and twice the length as compared to the original wire is used then the heat developed in it will be -

The equivalent resistance between A and B is ____________.

The gyro-magnetic ratio of an electron in an H-atom, according to Bohr model, is ______.

1. independent of which orbit it is in.
2. negative.
3. positive.
4. increases with the quantum number n.

An electron and a positron are released from (0, 0, 0) and (0, 0, 1.5R ) respectively, in a uniform magnetic field B = B0î, each with an equal momentum of magnitude p = e BR. Under what conditions on the direction of momentum will the orbits be non-intersecting circles?

An electron with angular momentum L moving around the nucleus has a magnetic moment given by ______.

Three point charges, + Q + 2Q and – 3Q are placed at the vertices of an equilateral triangle ABC of side l. If these charges are displaced to the mid-point A₁, B₁ and C₁, respectively, find the amount of the work done in shifting the charges to the new locations.

Write the relation between the velocity of propagation and the magnitudes of electric and magnetic fields.

In a hydrogen atom, the electron and proton are bound at a distance of about 0.53 Å:

(a) Estimate the potential energy of the system in eV, taking the zero of the potential energy at infinite separation of the electron from proton.

(b) What is the minimum work required to free the electron, given that its kinetic energy in the orbit is half the magnitude of potential energy obtained in (a)?

(c) What are the answers to (a) and (b) above if the zero of potential energy is taken at 1.06 Å separation?