Atoms — Physics STD 12 Science — Question

A hole diffuses from the p-side to the n-side in a p-n junction. This means that.

1. A bond ia broken on the n-side and the electron freed from the bond jumps to the conduction band.
2. A conduction electron on the p-side jumps to a broken bond to complete it.
3. A bond is broken on the n-side and the electron freed from the bond jumps to a broken bond on the p-side to complete it.
4. A bond is broken on the p-side and the electron freed from the bond jumps to a broken bond on the n-side to complete it.

In a dc motor, induced e.m.f. will be maximum(a) When motor takes maximum speed(b) When motor starts rotating(c) When speed of motor increases(d) When motor is switched off

The hyperfine lines in the spectrum is related to:

Why is the Wheatstone bridge better than the other methods of measuring resistances?

In comparison to a half wave rectifier, the full wave rectifier gives lower(a) Efficiency(b) Average dc(c) Average output voltage(d) None of these

In a diode valve the cathode temperature must be (f = work function)(a) High and ∅  should be high(b) High and ∅ should be low(c) Low and ∅ should be high(d) Low and ∅ should be high

Assertion  :   At a point in space, the electric field points towards north. In the region, surrounding this point the rate of change of potential will be zero along the east and west.
Reason     : Electric field due to a charge is the space around the charge.(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.