Moving Charges and Magnetism — Physics STD 12 Science — Question

A triode is operated in the linear region of its characteristics. If the plate voltage is slightly increased, the dynamic plate resistance will:

1. Increase.
2. Decrease.
3. Remain almost the same.
4. Become zero.

When cells are connected in parallel, then

(a) The current decreases	(b) The current increases
(c) The e.m.f. increases	(d) The e.m.f. decreases

The first model of atom in 1898 was proposed by:

__________ is Ohm's law for good conductor.

In a Young's experiment, the distance between two slits is 0.2 mm . If the wavelength of light used in this experiment is 5000 Å, then the distance of 3 rd bright fringes from central maxima will be __________ .

Refractive index of air is 1.0003. The correct thickness of air column which will have one more wavelength of yellow light (6000 Å) than in the same thickness in vacuum is

(a) 2 mm

(b) 2 cm

(c) 2 m

(d) 2 km

In a transformer 220 ac voltage is increased to 2200 volts. If the number of turns in the secondary are 2000, then the number of turns in the primary will be

(a) 200

(b) 100

(c) 50

(d) 20

Intensity of an electric field E due to a dipole, depends on distance r as

(a) E ∝

(b) E ∝

(c) E ∝

(d) E ∝

Curies law can be written as

(a) x ∝ (T -

(b) x ∝

(c) x ∝

(d) x ∝ T