ISC (Science) ISC Class 12 - CISCE Question Bank Solutions

In a potentiometer, a cell is balanced against 110 cm when the circuit is open. A cell is balanced at 100 cm when short-circuited through a resistance of 10 Ω. Find the internal resistance of the cell.

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

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.

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 

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: 

The intensity of the electric field at a point at a perpendicular distance ‘r’ from an infinite line charge, having linear charge density ‘λ’ is given by:

A charged oil drop weighing 1.6 x 10^-15 N is found to remain suspended in a uniform electric field of intensity 2 x 10³ Nc^-1. Find the charge on the drop. 

The focal length of a concave lens is 20 cm. The focal length of a convex lens is 25 cm. These two are placed in contact with each other. What is the power of the combination? Is it diverging, converging or undeviating in nature?

In case of an infinite line charge, how does intensity of electric field at a point change, if at all, when.

1. charge on it is doubled?
2. distance of the point is halved?

The focal length of a double convex lens is equal to the radius of curvature of either surface. What is the refractive index of its material?

A coil of self-inductance 2.5H and resistance 20Ω is connected to a battery of emf 120V having the internal resistance of 5 n. Find:

1) The time constant of the circuit.

2) The current in the circuit in steady state

The intensity of the electric field at a perpendicular distance of 0·5 m from an infinitely long line charge having linear charge density (λ) is 3-6 × 10³ Vm^-1. Find the value of λ.

A short electric dipole (which consists of two point charges, +q and -q) is placed at the centre 0 and inside a large cube (ABCDEFGH) of length L, as shown in Figure 1. The electric flux, emanating through the cube is:

a) `q"/"4piin_9L`

b) zero

c) `q"/"2piin_0L`

d) `q"/"3piin_0L`

Derive an expression for the intensity of electric field at a point in broadside position or on [4)
an equatorial line of an electric dipole.

Two-point charges Q₁ = 400 μC and Q₂ = 100 μC are kept fixed, 60 cm apart in a vacuum. Find the intensity of the electric field at the midpoint of the line joining Q₁ and Q₂.  

In an electric dipole, at which point is the electric potential zero ? 

Show that intensity of electric field at a point in broadside position of an electric dipole is given by:

E = `(1/(4 pi epsilon_0)) p/((r^2 + l^2)^(3//2))`

Where the terms have their usual meaning.

In an electric dipole, what is the locus of a point having zero potential?

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

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

Two infinitely long current carrying conductors X and Y are kept parallel to each other, 24 cm apart in a vacuum. They carry currents of 5A and 7A respectively, in the same direction, as shown in the figure below. Find the position of a neutral point, i.e., a point where resultant magnetic flux density is zero. (Ignore earth’s magnetic field).