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

The cyclotron frequency of an electron grating in a magnetic field of 1 T is approximately

(a) 28 MHz

(b) 280 MHz

(c) 2.8 GHz

(d) 28 GHz

Ratio between total intensity of magnetic field at equator to poles is

(a) 1 : 1

(b) 1 : 2

(c) 2 : 1

(d) 1 : 4

What should be the current in a circular coil of radius 5cm to annul  

(a) 0.4 A

(b) 4 A

(c) 40 A

(d) 1 A

Consider sunlight incident on a slit of width 10⁴A. The image seen through the slit shall.

In a capacitor of capacitance 20 μF, the distance between the plates is 2mm. If a dielectric slab of width 1mm and dielectric constant 2 is inserted between the plates, then the new capacitance is

(a) 2 μF

(b) 15.5 μF

(c) 26.6 μF

(d) 32 μF

Shown in the figure here is a convergent lens placed inside a cell filled with a liquid. The lens has focal length + 20 cm when in air and its material has refractive index 1.50. If the liquid has refractive index 1.60, the focal length of the system is

(a) + 80 cm

(b) – 80 cm

(c) – 24 cm

(d) –100 cm

The smallest temperature difference that can be measured with a combination of a thermocouple of thermo e.m.f. 30mV per degree and a galvanometer of 50 ohm resistance, capable of measuring a minimum current of  3 × 10^–7 amp is

(a) 0.5 degree

(b) 1.0 degree

(c) 1.5 degree

(d) 2.0 degree

When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom:

In the figure, shown the magnetic induction at the centre of there arc due to the current in portion AB will be

(a)

(b)

(c)

(d) Zero

Which of the following is correct when one cell is wrongly connected in series circuit?