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

Beams of electrons and protons move parallel to each other in the same direction. They ______.

A cell of emf E is connected across an external resistance R. When current 'I' is drawn from the cell, the potential difference across the electrodes of the cell drops to V. The internal resistance 'r' of the cell is ______.

The focal lengths of the objective and the eye-piece of a compound microscope are 1.0 cm and 2.5 cm respectively. Find the tube length of the microscope for obtaining a magnification of 300.

An electric dipole of dipole moment 2 × 10^-8 C-m in a uniform electric field experiences a maximum torque of 6 × 10^-4 N-m. The magnitude of the electric field is ______.

An electric dipole of length 2 cm is placed at an angle of 30° with an electric field 2 × 10⁵ N/C. If the dipole experiences a torque of 8 × 10^-3 Nm, the magnitude of either charge of the dipole is ______.

Two long parallel wires kept 2 m apart carry 3A current each, in the same direction. The force per unit length on one wire due to the other is ______.

Depict the orientation of an electric dipole in (a) stable and (b) unstable equilibrium in an external uniform electric field. Write the potential energy of the dipole in each case.

Three cells, each of emf E but internal resistances 2r, 3r and 6r are connected in parallel across a resistor R.

Obtain expressions for (i) current flowing in the circuit, and (ii) the terminal potential differences across the equivalent cell.

In a compound microscope an object is placed at a distance of 1.5 cm from the objective of focal length 1.25 cm. If the eye-piece has a focal length of 5 cm and the final image is formed at the near point, find the magnifying power of the microscope.

Two long straight parallel current-carrying conductors are kept ‘a’ distant apart in the air. The direction of current in both the conductors is the same. Find the magnitude of force per unit length and the direction of the force between them. Hence define one ampere.

What is mass defect?

Plot a graph showing variation of de Broglie wavelength λ versus `1/sqrtV` , where V is accelerating potential for two particles A and B, carrying the same charge but different masses m₁, m₂ (m₁ > m₂). Which one of the two represents a particle of smaller mass and why?

When monochromatic light is incident on a surface separating two media, the reflected and refracted light both have the same frequency as the incident frequency.

When is H_α line in the emission spectrum of hydrogen atom obtained? Calculate the frequency of the photon emitted during this transition.

A proton and an α -particle are accelerated through the same potential difference. Which one of the two has greater de-Broglie wavelength Justify your answer.

A proton and an α-particle are accelerated through the same potential difference. Which one of the two has less kinetic energy? Justify your answer.

State any two causes of energy loss in actual transformers.

A proton and an α-particle have the same de-Broglie wavelength. Determine the ratio of their accelerating potentials

Two spherical bobs, one metallic and the other of glass, of the same size are allowed to fall freely from the same height above the ground. Which of the two would reach earlier and why?

A proton and a deuteron are accelerated through the same accelerating potential. Which one of the two has the greater value of de-Broglie wavelength associated with it, and Give reasons to justify your answer.