Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

The electric field lines are crowded where electric field is:

A non-planar loop of conducting wire carrying a current I is placed as shown in the figure. Each of the straight sections of the loop is of length 2a. The magnetic field due to this loop at the point P (a,0,a) points in the direction

(a)

(b)

(c)

(d)

For a given temperature difference, which of the following pairs will generate maximum thermo e.m.f.

(a) Antimony-bismuth

(b) Silver-gold

(c) Iron-copper

(d) Lead-nickel

What causes spectral lines?

Gases begin to conduct electricity at low pressure because

(a) At low pressure, gases turn to plasma

(b) Colliding electrons can acquire higher kinetic energy due to increased mean free path leading to ionisation of atoms

(c) Atoms break up into electrons and protons

(d) The electrons in atoms can move freely at low pressure

The de-Broglie wavelength of a neutron at 27^oC is l. What will be its wavelength at 927^oC

(a) l / 2

(b) l / 3

(c) l / 4

(d) l / 9

A circular loop of radius 0.0157m carries a current of 2.0 amp. The magnetic field at the centre of the loop is (

(a) 1.57	(b) 8.0
(c) 2.5	(d)  3.14

In which radioactive disintegration, neutron dissociates into proton and electron

(a)  emission

(b) β - emission

(c) γ - emission

(d) Positron emission

Optoelectronic devices work on:

A positively charged particle moving in east direction enters a region of uniform magnetic field directed vertically upwards. What will be the path of the particle?