Science (English Medium) इयत्ता १२ - CBSE Question Bank Solutions

A parallel plate capacitor (A) of capacitance C is charged by a battery to voltage V. The battery is disconnected and an uncharged capacitor (B) of capacitance 2C is connected across A. Find the ratio of final charges on A and B.

A galvanometer shows full-scale deflection for current I_g. A resistance R₁ is required to convert it into a voltmeter of range (0 - V) and a resistance R₂ to convert it into a voltmeter of range (0 - 2V). Find the resistance of the galvanometer.

How is current sensitivity increased?

Read the following paragraph and answer the questions.

1. Find the equivalent capacitance between points A and B in the given diagram.
   
2. A dielectric slab is inserted between the plates of the parallel plate capacitor. The electric field between the plates decreases. Explain.
3. A capacitor A of capacitance C, having charge Q is connected across another uncharged capacitor B of capacitance 2C. Find an expression for (a) the potential difference across the combination and (b) the charge lost by capacitor A.
   OR
   Two slabs of dielectric constants 2K and K fill the space between the plates of a parallel plate capacitor of plate area A and plate separation d as shown in the figure. Find an expression for the capacitance of the system.
    

• Assertion (A): The given figure does not show a balanced Wheatstone bridge.
• Reason (R): For a balanced bridge small current should flow through the galvanometer.

Obtain the equivalent capacitance of the network shown in the figure. For a 300 V supply, determine the charge on each capacitor.

A charge 'q' is moved from a point A above a dipole of dipole moment 'p' to a point B below the dipole in equatorial plane without acceleration. Find the work done in the process.

(a) Write the basic nuclear process involved in the emission of β⁺ in a symbolic form, by a radioactive nucleus.

(b) In the reactions given below:

(i)`""_16^11C->_y^zB+x+v`

(ii)`""_6^12C+_6^12C->_a^20 Ne + _b^c He`

Find the values of x, y, and z and a, b and c.

Derive the mathematical expression for law of radioactive decay for a sample of a radioactive nucleus

How is the mean life of a given radioactive nucleus related to the decay constant?

When is a transistor said to be in active state?

Explain briefly the process of charging a parallel plate capacitor when it is connected across a d.c. battery

Obtain the relation between the decay constant and half life of a radioactive sample.

Define the terms :Current amplification factor. How are these determined using typical input and output characteristics?

Write symbolically the process expressing the β⁺ decay of `""_11^22Na`. Also write the basic nuclear process underlying this decay.

Light waves each of amplitude "a" and frequency "ω", emanating from two coherent light sources superpose at a point. If the displacements due to these waves are given by y₁ = a cos ωt and y₂ = a cos(ωt + ϕ) where ϕ is the phase difference between the two, obtain the expression for the resultant intensity at the point.

Why is it found experimentally difficult to detect neutrinos in nuclear β-decay?

Considering the case of a parallel plate capacitor being charged, show how one is required to generalize Ampere's circuital law to include the term due to displacement current.

What is the force of repulsion if each sphere is charged double the above amount, and the distance between them is halved?

Suppose the spheres A and B in Exercise 1.12 have identical sizes. A third sphere of the same size but uncharged is brought in contact with the first, then brought in contact with the second, and finally removed from both. What is the new force of repulsion between A and B?