Semiconductor Electronics: Materials, Devices and Simple Circuits — Physics STD 12 Science — Question

Identify the quantity which changes when a charged particle moves through a magnetic field?

Shown below is a distribution of charges. The flux of electric field due to these charges through the surface S is

(a) 3q/

(b) 2q/

(c) q/

(d) Zero

Which of the following statements concerning the depletion zone of an unbiased PN junction is (are) true

(a) The width of the zone is independent of the densities of the dopants (impurities)

(b) The width of the zone is dependent on the densities of the dopants

(c) The electric field in the zone is produced by the ionized dopant atoms

(d) b, c

When an electron in hydrogen atom is excited, from its 4^th to 5^th stationary orbit, the change in angular momentum of electron is (Planck’s constant: h = 6.6  

(a) 4.16	(b) 3.32
(c) 1.05	(d) 2.08

Four plates of the same area of cross-section are joined as shown in the figure. The distance between each plate is d. The equivalent capacity across A and B will be

(a)

(b)

(c)

(d)

The positive terminal of 12V battery is connected to the ground. Then the negative terminal will be at:

The minimum energy required for the electron emission from the metal surface can be supplied to the free electrons by which of the following physical processes?

Assertion  :   Leclanche cell is used, when constant supply of electric current is not required.  

Reason     : The e.m.f. of a Leclanche cell falls, if it is used continuously.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

What is the phase difference between electric and magnetic fields in an electromagnetic wave?