Current Electricity — Physics STD 12 Science — Question

As the temperature of a conductor increases, its resistivity and conductivity change. The ratio of resistivity to conductivity:

For non-conductors, the energy gap is

(a) 6 eV

(b) 1.1 eV

(c) 0.8 eV

(d) 0.3 eV

10cm is a wavelength corresponding to the spectrum of:

A beam of light AO is incident on a glass slab (μ = 1.54)  in a direction as shown in figure. The reflected ray OB is passed through a Nicol prism on viewing through a Nicole prism, we find on rotating the prism that

(a) The intensity is reduced down to zero and remains zero

(b) The intensity reduces down some what and rises again

(c) There is no change in intensity

(d) The intensity gradually reduces to zero and then again increases

The variation of anode current in a triode corresponding to a change in grid potential at three different values of the plate potential is shown in the diagram. The mutual conductance of the triode is

(a) 2.5 m mho

(b) 5.0 m mho

(c) 7.5 m mho

(d) 10.0 m mho

Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact convex. The effective power of the combination is

(a) 45 dioptres

(b) 9 dioptres

(c) 1/9 dioptre

(d) 6 dioptres

The state of photo-electrons emerging from the metal surface can be :

The length of a wire required to manufacture a solenoid of length l and self-induction L is (cross-sectional area is negligible)

Which of the following is true for number of spectral lines in going form Layman series to Pfund series

(a) Increases	(b) Decreases
(c) Unchanged	(d) May decreases or increases

X-ray beam can be deflected:

1. By an electric field.
2. By a magnetic field.
3. By an electric field as well aa by a magnetic field.
4. Neither by an electric field nor by a magnetic field.