Current Electricity — Physics STD 12 Science — Question

A potential difference of 42,000 volts is used in an X-ray tube to accelerate electrons. The maximum frequency of the X–radiations produced is  (1 eV = 1.6  and h = 6.63

(a)

(b)

(c)

(d)

A light bulb, a capacitor and a battery are connected together as shown here, with switch S initially open. When the switch S is closed, which one of the following is true

(a) The bulb will light up for an instant when the capacitor starts charging

(b) The bulb will light up when the capacitor is fully charged

(c) The bulb will not light up at all

(d) The bulb will light up and go off at regular intervals

Choose the correct statement:

An electron (mass = 9.1   kg; charge = 1.6   C) experiences no deflection if subjected to an electric field of 3.2   V/m, and a magnetic fields of 2.0   Wb/m². Both the fields are normal to the path of electron and to each other. If the electric field is removed, then the electron will revolve in an orbit of radius

(a) 45 m

(b) 4.5 m

(c) 0.45 m

(d) 0.045 m

M_x and M_y denote the atomic masses of the parent and the daughter nuclei respectively in a radioactive decay. The Q-value for a β^- decay is Q₁ and that for a β⁺ decay is Q₂. If me denotes the mass of an electron, then which of the following statements is correct?

The diagram shows-the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy

(a) I

(b) II

(c) III

(d) IV

When current passes through the circuit a compass needle rests in which direction (with respect to the Earth)?

When a positive q charge is taken from lower potential to a higher potential point, then its potential energy will

(a) Decrease

(b) Increases

(c) Remain unchanged

(d) Become zero