Moving Charges and Magnetism — Physics STD 12 Science — Question

A galvanometer with a resistance of 12 W gives full scale deflection when a current of 3 mA is passed. It is required to convert it into a voltmeter which can read up to 18 V.  the resistance to be connected is

(a) 6000 W

(b) 5988 W

(c) 5000 W

(d) 4988 W

Rest mass energy of an electron is 0.51 MeV. If this electron is moving with a velocity 0.8 c (where c is velocity of light in vacuum), then kinetic energy of the electron should be.

(a) 0.28 MeV

(b) 0.34 MeV

(c) 0.39 MeV

(d) 0.46 MeV

Wave front means:

A circular disc of which 2/3 part is coated with yellow and 1/3 part is with blue. It is rotated about its central axis with high velocity, then it will be seen as

(a) Green

(b) Brown

(c) White

(d) Violet

Which of the following cannot be used in electronic devices?

Electrons are emitted by a hot filament and are accelerated by an electric field, as shown in the figure. The two stops at the left ensure that the electron beam has a uniform cross-section.

1. The speed of the electrons is more at B than at A.
2. The electric current is from left to right.
3. The magnitude of the current is larger at B than at A.
4. The current density is more at B than at A.

A galvanometer of 100 Ω resistance gives full scale deflection when 10 mA of current is passed. To convert it into 10 A  range ammeter, the resistance of the shunt required will be

(a) -10 Ω

(b) 1 Ω

(c) 0.1 Ω

(d) 0.01 Ω

The slits in a Young's double slit experiment have equal width and the source is placed symmetrically with respect to the slits. The intensity at the central fringe is I₀. If one of the slits is closed, the intensity at this point will be: