Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

Download the PDF Sample Papers Free for off line practice and view the Solutions online.

ISC Class 12 Physics Solved Question Paper 2009

Short Answer Type

21.

(i) What is meant by:

(1) Drift velocity and

(2) Relaxation time?

(ii) A metallic plug AB is carrying a current I (see Figure 4 below). State how the drift velocity of free electrons varies, if at all, from end A to end B.

1040 Views

22. Figure below shows a uniform manganin wire XY of length 100 cm and resistance 9 Ω, connected to an accumulator D of emf 4 V and internal resistance 1 Ω through a variable resistance R. E is sa cell of emf 1.8 V connected to the wire XY via a jockey J and a central zero galvanometer G. It is found that the galvanometer shows no deflection when XJ = 80 cm. Find the value of R.

292 Views

23. Obtain an expression for magnetic flux density ‘B’ at the center of a circular coil of radius R and having N turns, when a current I is flowing through it.

472 Views

24.

(i) State any two differences between a moving coil galvanometer and a tangent galvanometer.

(ii) What is the use of a Cyclotron?

475 Views

25. What is meant by the time constant of an LR circuit? When the current flowing through a coil P decreases from 5A to 0 in 0.2 seconds, an emf of 60 V is induced across the terminals of an adjacent coil Q. Calculate the coefficient of mutual inductance of the two coils P and Q.

214 Views

26.
When an alternating emf e = 300 Sin (100 πt + π/6) Volt is applied to a circuit, the current I through it is I = 5.0 Sin (100 πt - π/6) ampere. Find the :

(i) Phase difference between the emf and the current.

(ii) Average power consumed by the circuit.

Given,

e = 300 Sin (100 πt + π/6);

I = 5.0 Sin (100 πt - π/6)

By comparing e = e₀ sin wt and I = I₀ sin wt

We find e₀ = 300 and I₀ = 5

(i) the phase difference between emf and current is 60°.

ii) Average power, P_av = $fraction numerator straight e subscript straight o space straight I subscript 2 over denominator 2 end fraction space equals space fraction numerator 300 space x space 5 over denominator 2 end fraction space equals space 750 space W$

379 Views

27. Obtain an expression for resonant frequency ‘f₀’of a series LCR circuit.

451 Views

28.

In which part of the electromagnetic spectrum, do the following radiations lie:

(i) Having wavelength of 20 nm

(ii) Having frequency of 10 MHz

274 Views

29. A thin convex lens which is made of glass (refractive index 1.5) has a focal length of 20 cm. It is now completely immersed in a transparent liquid having refractive index 1.75. Find the new focal length of the lens.

444 Views