Nuclei — Physics STD 12 Science — Question

For germanium diode, the junction voltage is about _____.

Three equal positive charges are kept at the corners of an equilateral triangle. What will be the vector sum of the forces acting on the particles?

The cold junction of a thermocouple is maintained at 10℃. No thermo e.m.f. is developed when the hot junction is maintained at 530 ℃ . The neutral temperature is

(a) 260℃

(b) 270℃

(c) 265℃

(d) 520℃

When the N-pole of a bar magnet points towards the south and S-pole towards the north, the null points are at the

(a) Magnetic axis	(b) Magnetic centre
(c) Perpendicular divider of magnetic axis	(d) N and S poles

A region surrounding a stationary electric dipoles has:

Which of the following particles will experience maximum magnetic force circle when projected with the same velocity perpendicular to a magnetic field?

1. Electron
2. Proton
3. He⁺
4. Li⁺⁺

A source of sound moves towards an observer.

1. The frequency of the source is increased.
2. The velocity of sound in the medium is increased.
3. The wavelength of sound in the medium towards the observer is decreased.
4. The amplitude of vibration of the particles is increased.

The charges 1, 2, 3 are moving in uniform transverse magnetic field then:

Assertion  :   X-rays are used for studying the structure of crystals.

Reason      : The distance between the atoms of crystals is of the order of wavelength of X-rays.

(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.

Which of the following is not true for wire wound resistor?