Atoms — Physics STD 12 Science — Question

If an electric current is passed through a nerve of a man, then man         

(a) Begins to laugh	(b) Begins to weep
(c) Is excited	(d) Becomes insensitive to pain

If a 0.1 % increase in length due to stretching, the percentage increase in its resistance will be

(a) 0.2 %

(b) 2 %

(c) 1 %

(d) 0.1 %

The power of a person's spectacle lenses is +2 D . He is suffering from which of the following defects?

When a comb rubbed with dry hair attracts pieces of paper. This is because the.

An electric dipole has a pair of equal and opposite point charges q and –q separated by a distance 2x. The axis of the dipole is:

The resistance of 10 metre long potentiometer wire is 1ohm/meter. A cell of e.m.f. 2.2 volts and a high resistance box are connected in series to this wire. The value of resistance taken from resistance box for getting potential gradient of 2.2 millivolt/metre will be

(a) 790 Ω

(b) 810 Ω

(c) 990 Ω

(d) 1000 Ω

In a nuclear reactor, moderators slow down the neutrons which come out in a fission process. The moderator used have light nuclei. Heavy nuclei will not serve the purpose because:

The shortest wavelength in the Lyman series of hydrogen spectrum is 912 Å corresponding to a photon energy of 13.6 eV. The shortest wavelength in the Balmer series is about

(a) 3648 Å

(b) 8208 Å

(c) 1228 Å

(d) 6566 Å

Which of the following shows that the earth behaves as a magnet?

Find the value of x in the following nuclear reaction.
₇​N¹⁴ + ₂​He⁴ → _x​O¹⁷ + _1​H¹