Electric Charges and Fields — Physics STD 12 Science — Question

Which of the following will produce maximum electromotive force?

The energy emitted by a source is in the form of:

An object is placed at a distance of f/2  from a convex lens. The image will be

(a) At one of the foci, virtual and double its size

(b) At 3f / 2, real and inverted

(c) At 2f, virtual and erect

(d) None of these

If the potential difference applied to the tube is doubled and the separation between the filament and the target is also doubled, the cutoff wavelength:

Two identical thin bar magnets each of length l and pole strength m are placed at right angle to each other with north pole of one touching south pole of the other. Magnetic moment of the system is

(a) ml

(b) 2ml

(c)

(d)

Solar energy is mainly caused due to

(a) Fission of uranium present in the sun

(b) Fusion of protons during synthesis of heavier elements

(c) Gravitational contraction

(d) Burning of hydrogen in the oxygen

In a radioactive reaction  , the number of α - particles emitted is

(a) 7

(b) 6

(c)  5

(d) 4

Which of the following are in the ascending order of wavelength?

In a semiconductor:

ike magnetic force ______ each other.