Semiconductor Electronic: Material, Devices And Simple Circuits — Physics STD 12 Science — Question

A beam of monochromatic blue light of wavelength 4200Å in air travels in water (μ = 4/3). Its wavelength in water will be

(a) 2800 Å

(b) 5600 Å

(c) 3150 Å

(d) 4000 Å

When no current is passed through a conductor:

1. The free electrons do not move.
2. The average speed of a free electron over a large period of time is zero.
3. The average velocity of a free electron over a large period of time is zero.
4. The average of the velocities of all the free electrons at an instant is zero.

If the capacitors having capacitance C₁ and C₂ are connected in parallel then their effective capacitance is given by:

A bulb of 100 watt is hanging at a height of one meter above the centre of a circular table of diameter 4 m. If the intensity at a point on its rim is , then the intensity at the centre of the table will be

(a)

(b) 2

(c) 2

(d) 5

In an AC circuit, the impedance is 3​ times the reactance, then the phase angle is.

The charge on a hole is equal to the charge of

(a) Zero

(b) Proton

(c) Neutron

(d) Electron

The current in a triode at anode potential 100 V and grid potential – 1.2 V is 7.5 mA. If grid potential is changed to – 2.2 V, the current becomes 5.5 mA. the value of trans conductance (g_m) will be

(a) 2 mili mho

(b) 3 mili mho

(c) 4 mili mho

(d) 0.2 mili mho

In interchanging the corresponding positions of battery and galvanometer in a Wheatstone bridge, the balanced position:

Electrons with energy 80 keV are incident on the tungsten target of an X-ray tube. K shell electrons of tungsten have ionization energy 72.5 keV. X-rays emitted by the tube contain only

(a) A continuous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of  ~ 0.155Å

(b) A continuous X-ray spectrum (Bremsstrahlung] with all wavelengths

(c) The characteristic X-rays spectrum of tungsten

(d) A continuous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of ~ 0.155Å and the characteristic X-ray spectrum of tungsten

The circuit shown in following figure contains two diode D₁ and D₂ each with a forward resistance of 50 ohms and with infinite backward resistance. If the battery voltage is 6 V, the current through the 100 ohm resistance (in amperes) is

(a) Zero

(b) 0.02

(c) 0.03

(d) 0.036