Science (English Medium) इयत्ता १२ - CBSE Question Bank Solutions for Physics

Draw a circuit diagram of an n-p-n transistor with its emitter-base junction forward biased and base-collector junction reverse biased. Briefly describe its working.
Explain how a transistor in its active state exhibits a low resistance at its emitter-base junction and high resistance at its base-collector junction.

Derive the expression for the voltage gain of a transistor amplifier in CE configuration in terms of the load resistance R_L, current gain β_a and input resistance.
Explain why input and output voltages are in the opposite phase.

State Gauss's law in electrostatics. Show, with the help of a suitable example along with the figure, that the outward flux due to a point charge 'q'. in vacuum within a closed surface, is independent of its size or shape and is given by `q/ε_0`

Answer the following question.
Draw the circuit arrangement for studying the output characteristics of an n-p-n transistor in CE configuration. Explain how the output characteristics is obtained.

State Gauss’s law on electrostatics and drive expression for the electric field due to a long straight thin uniformly charged wire (linear charge density λ) at a point lying at a distance r from the wire.

Define the term ‘resolving power of a telescope’. 

A uniform magnetic field of 3000 G is established along the positive z-direction. A rectangular loop of sides 10 cm and 5 cm carries a current of 12 A. What is the torque on the loop in the different cases shown in fig.? What is the force on each case? Which case corresponds to stable equilibrium?

The instrument for the accurate measurement of the e.m.f of a cell is ______.

Kirchhoff’s second law is a consequence of law of conservation of ______.

Figure shows current in a part of an electrical circuit. Then current I is ______.

Consider the motion of a charged particle in a uniform magnetic field directed into the paper. If velocity v of the particle is in the plane of the paper the charged particle will ______.

Considering the magnetic field of the earth, the correct relation of the geographic pole and the magnetic pole is ______.

Sodium and copper have work function 2.3 eV and 4.5 eV respectively. Then, the ratio of the wavelengths is nearest to ______.

Nuclear mass M is found to be ______.

Correct expression for mass defect Δm is ______.

The Gaussian surface ______.

Assertion: Kirchhoff’s junction rule follows from conservation of charge.
Reason: Kirchhoff’s loop rule follows from conservation of momentum.