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

Two a-particles have the ratio of their velocities as 3 : 2 on entering the field. If they move in different circular paths, then the ratio of the radii of their paths is ______.

A cylinder of radius R and length L is placed in a uniform electric field E parallel to the cylinder axis. The total flux for the surface of the cylinder is given by ______.

An electric charge q is placed at the centre of a cube of side a. The electric flux on one of its faces will be ______.

Total electric flux coming out of a unit positive charge kept in air is ______.

The electric field intensity due to an infinite cylinder of radius R and having charge q per unit length at a distance rir r(r > R) from its axis is ______.

A point charge q is placed at a distance a/2 directly above the centre of a square of side a. The electric flux through the square is ______.

A straight line plot showing the terminal potential difference (V) of a cell as a function of current (I) drawn from it, is shown in the figure. The internal resistance of the cell would be then ______.

What will be the total flux through the faces of the cube (figure) with side of length a if a charge q is placed at

1. A: a corner of the cube.
2. B: mid-point of an edge of the cube.
3. C: centre of a face of the cube.
4. D: mid-point of B and C.

Two batteries of emf ε₁ and ε₂ (ε₂ > ε₁) and internal resistances r₁ and r₂ respectively are connected in parallel as shown in figure.

A cell of emf E and internal resistance r is connected across an external resistance R. Plot a graph showing the variation of P.D. across R, versus R.

An object approaches a convergent lens from the left of the lens with a uniform speed 5 m/s and stops at the focus. The image ______.

Will the focal length of a lens for red light be more, same or less than that for blue light?

An unsymmetrical double convex thin lens forms the image of a point object on its axis. Will the position of the image change if the lens is reversed?

In many experimental set-ups the source and screen are fixed at a distance say D and the lens is movable. Show that there are two positions for the lens for which an image is formed on the screen. Find the distance between these points and the ratio of the image sizes for these two points.

A particle is dropped from a height H. The de Broglie wavelength of the particle as a function of height is proportional to ______.

A proton, a neutron, an electron and an α-particle have same energy. Then their de Broglie wavelengths compare as ______.

An electron is moving with an initial velocity `v = v_0hati` and is in a magnetic field `B = B_0hatj`. Then it’s de Broglie wavelength ______.

An electron (mass m) with an initial velocity `v = v_0hati (v_0 > 0)` is in an electric field `E = - E_0hati `(E₀ = constant > 0). It’s de Broglie wavelength at time t is given by ______.

An electron (mass m) with an initial velocity `v = v_0hati` is in an electric field `E = E_0hatj`. If λ₀ = h/mv₀, it’s de Broglie wavelength at time t is given by ______.

Relativistic corrections become necessary when the expression for the kinetic energy `1/2 mv^2`, becomes comparable with mc², where m is the mass of the particle. At what de Broglie wavelength will relativistic corrections become important for an electron?

1. λ = 10 nm
2. λ = 10^–1 nm
3. λ = 10^–4 nm
4. λ = 10^–6 nm