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

Calculate equivalent capacitance of the circuit shown in the Figure given below:

Calculate electric potential at a point P which is at a distance of 9 cm from a point charge of 50 μC.

If potential difference between the two ends of a metallic wire is doubled, drift speed of free electrons in the wire ______.

A dielectric slab of dielectric constant K and thickness t is introduced between the two plates of a capacitor of plate-separation d (>t) and common area A. The capacitance of this system is given as:

`C = (∈_o"A")/((d-t)+(t/k))`

How does the capacitance C modify in each of the following cases?

1. The dielectric slab covers half the distance of separation between the two plates.
2. The whole space between the plates is filled with the dielectric.

The order of coloured rings in a carbon resistor is red, yellow, blue and silver. The resistance of the
carbon resistor is:

a) 24 x 10⁶ Ω ± 5%

b) 24 x 10⁶ Ω ± 10%

c) 34 x 10⁴ Ω ± 10%

d) 26 x 10⁴ Ω ± 5%

In a potentiometer experiment, balancing length is found to be 120 cm for a cell E₁ of emf 2V. What will be the balancing length for another cell E₂ of emf 1.5V? (No other changes are made in the experiment.)

Define current density. Write an expression which connects current density with drift speed

Calculate force per unit length acting on the wire B due to the current flowing in the wire A.(See
Figure 2 below)

ε₁ and ε₂ are two batteries having emf of 34V and 10V respectively and internal resistance of 1Ω and 2Ω respectively. They are connected as shown in the figure below. Using Kirchhoff’s Laws of electrical networks, calculate the currents I₁ and I₂.

An electrical bulb is marked 200V, 100W. Calculate the electrical resistance of its filament. If five such
bulbs are connected in series to a 200V supply, how much current will flow through them?

The equivalent resistance between points. a and f of the network shown in Figure 2 is :

a) 24 Ω

b) 110 Ω

c) 140 Ω

d) 200 Ω

A resistor R is connected to a cell of-emf e and internal resistance r. The potential difference across the resistor R is found to be V. State the relation between e, V, Rand r.

Three identical cells each of emf 2V and internal resistance 10 Ω are connected in series to form a battery. The battery is then connected to a parallel combination of two identical resistors, each of resistance 6 Ω. Find the current delivered by the battery.

Draw labelled graphs to show how electrical resistance varies with temperature for: 

1) a metallic wire.

2) a piece of carbon

Two resistors R1 = 400Ω and R₂ = 20 n are connected in parallel to a battery. If heating the power developed in R₁ is 25 W. find the heating power developed in R₂

With the help of a labelled diagram, show that the balancing condition of a Wheatstone bridge is

`"R"_1/"R"_2 = "R"_3/"R"_4` where the terms have their usual meaning.

An I0m long uniform metallic wire having a resistance of 20Ω IS used as a  potentiometer wire. This wire is connected in series with another resistance of 480Ω
and a battery of emf 5V having negligible internal resistance. If an unknown emf e is balanced across 6m of the potentiometer wire, calculate

1) the potential gradient across the potentiometer wire

2) the value of the unknown emf e.

In a series LCR circuit, what is the phase difference between V_L and V_C where V_L is the potential difference across the inductor and V c is the potential difference across the capacitor?

In a potentiometer experiment, the balancing length with a resistance of 2Ω is found to be 100 cm, while that of an unknown resistance is 500 cm. Calculate the value of the unknown resistance. 

Obtain the balancing  condition for the Wheatstone bridge arrangements as shown in Figure 4 below: