ISC (Science) ISC Class 12 - CISCE Important Questions for Physics (Theory)

What is meant by the statement: "Relative permittivity of water is 81"?

Can a body be given a charge of 2.2 × 10^-19 C? Give a reason for your answer.

Arrangement of an oxygen ion and two hydrogen ions in a water molecule is shown in figure below.

Calculate electric dipole moment of water molecule. Express your answer in terms of e (charge on hydrogen ion), l and θ.

“A uniformly charged conducting spherical shell for the points outside the shell behaves as if the entire charge of the shell is concentrated at its centre”. Show this with the help of a proper diagram and verify this statement.

Obtain an expression for an intensity of electric field at a point at the end of position, i.e., the axial position of an electric dipole.

x

Deduce an expression for equivalent capacitance C when three capacitors C₁, C₂ and C₃ connected in parallel.

Two point charges of 10C each are kept at a distance of 3m in the vacuum. Calculate their electrostatic potential energy.

Four capacitors, C₁, C₂, C₃ andC₄ are connected as shown in Figure 3 below. Calculate equivalent capacitance of the circuit between points X . and Y.

Figure 4 below shows a capacitor C, an inductor L and a resistor R, connected in series
to an a.c. supply of 220 V

Calculate:

1) The resonant frequency of the given CLR circuit.

2) Current flowing through·the circuit.

3) Average power consumed by the circuit.

Define equipotential surface. 

Obtain an expression for electric potential ‘V’ at a point in an end-on position i.e. axial position of the electric dipole. 

Three capacitors of capacitance `C_1 = 3muf` , `C_2 = 6muf` , `C_3 = 10muf` , are connected to a 10V battery as shown in figure 3 below : 

Calculate :

(a) Equivalent capacitance.

(b) Electrostatic potential energy stored in the system 

The electrostatic potential energy of two-point charges, 1 µC each, placed 1 meter apart in the air is: 

A wire of resistance 'R' is cut into 'n' equal parts. These parts are then connected in parallel with each other. The equivalent resistance of the combination is : 

Show that electric potential at a point P, at a distance 'r' from a fixed point charge Q, is given by:
    `v=(1/(4pi∈_0))Q/r`.

Three capacitors C₁ = 3μF, C₂ = 6μF, and C₃ = 10μF are connected to a 50 V battery as  shown in Figure  below:

Calculate:
(i) The equivalent capacitance of the circuit between points A and B.
(ii) The charge on C₁.

A parallel plate air capacitor has a capacitance of  5 μF. It becomes 50 μF when a dielectric medium occupies the entire space between its two plates. What is the dielectric constant of the medium?

AB and CD are two parallel conductors kept 1 m apart and connected by a resistance R of 6 Ω as shown in Figure below. They are placed in a magnetic field B = 3 × 10^-2 T which is perpendicular to the plane of the conductors and directed into the paper. A Wire. MN is placed over AB and CD. and then made to slide with a velocity 2 ms^-1 (Neglect the resistance of AB, CD, and MN.)

Calculate the induced c.urrent flowing through the resistor R.

You are provided with 8 μF capacitors. Show with the help of a diagram how you will arrange minimum number of them to get a resultant capacitance of 20 μF.

What is meant by an equipotential surface?