PUC Science 2nd PUC Class 12 - Karnataka Board PUC Question Bank Solutions for Physics

The energy levels of an atom are as shown below. Which of them will result in the transition of a photon of wavelength 275 nm?

Which transition corresponds to emission of radiation of maximum wavelength?

The charge on a proton is +1.6 × 10⁻¹⁹ C and that on an electron is −1.6 × 10⁻¹⁹ C. Does it mean that the electron has 3.2 × 10⁻¹⁹ C less charge than the proton? 

When the separation between two charges is increased, the electric potential energy of the charges

The electric field at the origin is along the positive x-axis. A small circle is drawn with the centre at the origin, cutting the axes at points A, B, C and D with coordinates (a, 0), (0, a), (−a, 0), (0, −a), respectively. Out of the points on the periphery of the circle, the potential is minimum at  

If a body is charged by rubbing it, its weight

Consider the situation in the figure. The work done in taking a point charge from P to Ais W_A, from P to B is W_B and from P to C is W_C. 

A point charge q is rotated along a circle in an electric field generated by another point charge Q. The work done by the electric field on the rotating charge in one complete revolution is 

The electric field and the electric potential at a point are E and V, respectively.  

Electric potential decreases uniformly from 120 V to 80 V, as one moves on the x-axis from x = −1 cm to x = +1 cm. The electric field at the origin 

(a) must be equal to 20 Vcm⁻¹
(b) may be equal to 20 Vcm⁻¹
(c) may be greater than 20 Vcm⁻¹
(d) may be less than 20 Vcm⁻¹ 

Which of the following quantities does not depend on the choice of zero potential or zero potential energy?

The electric field in a region is directed outward and is proportional to the distance rfrom the origin. Taking the electric potential at the origin to be zero, 

When a current is established in a wire, the free electrons drift in the direction opposite to the current. Does the number of free electrons in the wire continuously decrease?

Electrons are emitted by a hot filament and are accelerated by an electric field, as shown in the figure. The two stops at the left ensure that the electron beam has a uniform cross-section.

A current of 1.0 A exists in a copper wire of cross-section 1.0 mm². Assuming one free electron per atom, calculate the drift speed of the free electrons in the wire. The density of copper is 9000 kg m^–3.

Consider a wire of length 4 m and cross-sectional area 1 mm² carrying a  current of 2 A. If each cubic metre of the material contains 10²⁹ free electrons, find the average time taken by an electron to cross the length of the wire.