Atoms — Physics STD 12 Science — Question

When the electron in the hydrogen atom jumps from 2^nd orbit to 1^st orbit, the wavelength of radiation emitted is 𝜆. When the electrons jump from 3^rd orbit to 1^st orbit, the wavelength of emitted radiation would be

(a)

(b)

(c)

(d)

In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit?

Curies law can be written as

(a) x ∝ (T -

(b) x ∝

(c) x ∝

(d) x ∝ T

Capacitance of a capacitor made by a thin metal foil is 2μF. If the foil is folded with paper of thickness 0.15 mm, dielectric constant of paper is 2.5 and width of paper is 400 mm , then length of foil will be

(a) 0.34 m

(b) 1.33 m

(c) 13.4 m

(d) 33.9 m

Assertion   :  In a simple battery circuit the point of lowest potential is positive terminal of the battery

Reason      : The current flows towards the point of the higher potential as it flows in such a circuit from the negative to the positive terminal.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Two point charges 2 C and -6 C attract each other with a force of 12 N. A negative charge of 2 C is added to each of the above charges, now the force between them is:

You are given several identical resistances each of value R = 10 Ω  and each capable of carrying maximum current of 1 ampere. It is required to make a suitable combination of these resistances to produce a resistance of  5 Ω which can carry a current of 4 amperes. The minimum number of resistances of the type R that will be required for this job

(a) 4

(b) 10

(c) 8

(d) 20

Assertion :   In all conductors, for studying the thermoelectric behaviour or metals, lead is taken as a reference metal.  

Reason    : In lead, the Thomson effect is negative.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

A radioactive material has an initial amount 16gm. After 120 days it reduces to 1gm, then the half-life of radioactive material is

(a) 60 days

(b) 30 days

(c) 40 days

(d) 240 days

A spherical ball is dropped in a long column of a viscous liquid. The speed of the ball as a function of time may be best represented by the graph:

1. A
2. B
3. C
4. D