Science (English Medium) Class 12 - CBSE Question Bank Solutions

Calculate the amplification factor of a triode valve that has plate resistance of 2 kΩ and transconductance of 2 millimho.

The plate resistance and amplification factor of a triode are 10kΩ and 20. The tube is operated at plate voltage 250 V and grid voltage −7.5 V. The plate current is 10 mA. (a) To what value should the grid voltage be changed so as to increase the plate current to 15 mA? (b) To what value should the plate voltage be changed to take the plate current back to 10 mA?

The plate current, plate voltage and grid voltage of a 6F6 triode tube are related as i_p = 41 (V_p + 7 V_g)^1.41

Here, V_p and V_g are in volts and i_p in microamperes.
The tube is operated at V_p = 250 V, V_g = −20 V. Calculate (a) the tube current, (b) the plate resistance, (c) the mutual conductance and (d) the amplification factor.

A triode has mutual conductance of 2.0 millimho and plate resistance of 20 kΩ. It is desired to amplify a signal by a factor of 30. What load resistance should be added in the circuit?

The figure shows two identical triode tubes connected in parallel. The anodes are connected together and the cathodes are connected together. Show that the equivalent plate resistance is half the individual plate resistance, the equivalent mutual conductance is double the individual mutual conductance and the equivalent amplification factor is the same as the individual amplification factor.

The intensity at the central maximum (O) in a Young’s double slit experimental set-up shown in the figure is I_O. If the distance OP equals one-third of the fringe width of the pattern, show that the intensity at point P, would equal `(I_0)/4`.

In Young’s double slit experiment, the slits are separated by 0.5 mm and screen is placed 1.0 m away  from the slit. It is found that the 5^th bright fringe is at a distance of 4.13 mm from the 2^nd dark fringe.  Find the wavelength of light used.  

An equilateral glass prism has a refractive index 1.6 in the air. Calculate the angle of minimum deviation of the prism, when kept in a medium of refractive index `4sqrt(2)"/"5.`

Answer the following question.
Describe any two characteristic features which distinguish between interference and diffraction phenomena. Derive the expression for the intensity at a point of the interference pattern in Young's double-slit experiment.

A carbon resistor is shown in the figure. Using color code, write the value of the resistance.

How does the angle of minimum deviation of a glass prism vary if the incident violet light is replaced by red light?

The ______, a property of materials C, Si, and Ge depends upon the energy gap between their conduction and valence bands.

Two cells of 1.25 V and 0.75 V are connected in series with anode of one connected to cathode of the other. The effective voltage will be ______.

The magnetic field lines ______.

If we have two coherent sources S₁ and S₂ vibrating in phase, then for an arbitrary point P constructive interference is observed whenever the path difference is ______.

A long, hollow conducting cylinder is kept coaxially inside another long, hollow conducting cylinder of larger radius. Both the cylinders are initially electrically neutral ______.

Consider a current carrying wire (current I) in the shape of a circle.

Assertion: Bending a wire does not effect electrical resistance.
Reason: Resistance of wire is proportional to resistivity of material.