Nuclei — Physics STD 12 Science — Question

If a magnet of pole strength m is divided into four parts such that the length and width of each part is half that of initial one, then the pole strength of each part will be(a) m/4(b) m/2(c) m/8(d) 4m

A freshly prepared radioactive source of half life 2 hr emits radiation of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with this source is:

Assertion  :   The 200 W bulbs glows with more brightness then 100 W bulbs.
Reason    : A 100 W bulb has more resistance than a 200 W bulb.(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 student wants to find if a star if moving away from the earth or towards the earth. Which of the following principle he can use? 

The explosion of the atomic bomb takes place due to(a) Nuclear fission(b) Nuclear fusion(c) Scattering(d) Thermionic emission

The only property possessed by ferromagnetic substance is(a) Hysteresis(b) Susceptibility(c) Directional property(d) Attracting magnetic substances

A Zener diode:

The direction of induced current is such that it opposes the very cause that has produced it. This is the law of(a) Lenz(b) Faraday(c) Kirchhoff(d) Fleming

If the current in the circuit for heating the filament is increased, the cutoff wavelength:

1. Will increase.
2. Will decrease.
3. Will remain unchanged.
4. Will change.