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

A small test charge is released at rest at a point in an electrostatic field configuration. Will it travel along the field line passing through that point?

What is the work done by the field of a nucleus in a complete circular orbit of the electron? What if the orbit is elliptical?

We know that electric field is discontinuous across the surface of a charged conductor. Is electric potential also discontinuous there?

Guess a possible reason why water has a much greater dielectric constant (= 80) than say, mica (= 6).

Name the junction diode whose I-V characteristics are drawn below: 

 How does the path followed by the charge get affected if its velocity has a component parallel to \[\vec{B}\] .

Velocity of light in glass is 2 × 10⁸ m/s and in air is 3 × 10⁸ m/s. If the ray of light passes from glass to air, calculate the value of critical angle.

Three point charges +q each are kept at the vertices of an equilateral triangle of side 'l'. Determine the magnitude and sign of the charge to be kept at its centroid so that the charges at the vertices remain in equilibrium.

Why must electrostatic field be normal to the surface at every point of a charged conductor?

Suppose a charged particle moves with a velocity v near a wire carrying an electric current. So, a magnetic force acts on it. If the same particle is seen from a frame moving with velocity v in the same direction, the charge will be found to be at rest. Will the magnetic force become zero in this frame?  Will the magnetic field become zero in this frame?

Figure shows a smooth pair of thick metallic rails connected across a battery of emf εhaving a negligible internal resistance. A wire ab of length l and resistance r can slide smoothly on the rails. The entire system lies in a horizontal plane and is immersed in a uniform vertical magnetic field B. At an instant t, the wire is given a small velocity vtowards right. (a) Find the current in it at this instant. What is the direction of the current? (b) What is the force acting on the wire at this instant? (c) Show that after some time the wire ab will slide with a constant velocity. Find this velocity.

V-I graph for a metallic wire at two different temperatures T1 and T2 is as shown in the figure. Which of the two temperatures is higher and why?

What is the ratio of the velocity of the wave in the two media of refractive indices μ1 and μ2?

A potential difference V is applied across a conductor of length L and diameter D. How is the drift velocity, v_d, of charge carriers in the conductor affected when (i) V is halved, (ii) L is doubled and (iii) D is halved ? justify your answer in each case.

The I-V characteristics shown in figure represent ______.

In an inertial frame of reference, the magnetic force on a moving charged particle is `vec"F"`. Its value in another inertial frame of reference will be ______.