Nuclei — Physics STD 12 Science — Question

To explain his theory, Bohr used

(a) Conservation of linear momentum

(b) Conservation of angular momentum

(c) Conservation of quantum frequency

(d) Conservation of energy

In an AC series circuit, the instantaneous current is zero when the instantaneous voltage is maximum. Connected to the source may be a:

1. Pure inductor.
2. Pure capacitor.
3. Pure resistor.
4. Combination of an inductor and a capacitor.

When light of wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, however light of 600 nm wavelength is sufficient for creating photoemission. What is the ratio of the work functions of the two emitters

(a) 1 : 2

(b) 2 : 1

(c) 4 : 1

(d) 1 : 4

How many electrons will there be in one coulomb of charge?

Consider the following two statements:

1. Linear momentum of the system remains constant.
2. Centre of mass of the system remains at rest.

1. ​​​​​​A implies B and B implies A.
2. A does not imply B and B does not imply A.
3. A implies B but B does not imply A.
4. B implies A but A does not imply B.

Forward biasing is that in which applied voltage:

Assertion :   Gauss theorem is not applicable in magnetism.

Reason    : Mono magnetic pole does not exist.

(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.

An X-ray tube is operating at 50 kV and 20 mA. The target material of the tube has a mass of 1.0 kg and specific heat 495 J kg^-1 . One percent of the supplied electric power is converted into X-rays and the entire remaining energy goes into heating the target. Then

(a) A suitable target material must have a high melting temperature

(b) The average rate of rise of temperature of target would be 2 °C/s

(c) The minimum wavelength of the X-rays emitted is about 0.25

(d) a, b, c

When a magnetic field is applied in a direction perpendicular to the direction of cathode rays, then their

(a) Energy decreases

(b) Energy increases

(c) Momentum increases

(d) Momentum and energy remain unchanged

In a tangent galvanometer a current of 0.1 A produces a deflection of 30^o. The current required to produce a deflection of 60^o is

(a) 0.2 A

(b) 0.3 A

(c) 0.4 A

(c) 0.5 A