Magnetism And Matter — Physics STD 12 Science — Question

One of the following wavelengths is absent and the rest are present in the X-rays coming from a Coolidge tube. Which one is the absent wavelength?

An achromatic combination of lenses is formed by joining

(a) 2 convex lenses	(b) 2 concave lenses
(c) 1 convex lens and 1 concave lens	(d) Convex lens and plane mirror

The thermo e.m.f. of a thermocouple varies with the temperature θ of the hot junction as   in volts where the ratio a/b is 700℃.  If the cold junction is kept at 0℃, then the neutral temperature is

(a) 700℃

(b) 350℃

(c) 1400℃

(d) No neutral temperature is possible for this thermocouple

An ammeter whose resistance is 180 Ω gives full scale deflection when current is 2 mA. The shunt required to convert it into an ammeter reading 20 mA (in ohms) is

(a) 18

(b) 20

(c) 0.1

(d) 10

Which is the factor that internal resistance does not depend on?

In which of the following decays the atomic number decreases?

A capacitor is charged by using a battery which is then disconnected. A dielectric slab is introduced between the plates which results in:

A molecule with a dipole moment p is placed in an electric field of strength E. Initially the dipole is aligned parallel to the field. If the dipole is to be rotated to be anti-parallel to the field, the work required to be done by an external agency is

(a) – 2pE

(b) – pE

(c) pE

(d) 2pE

The resistance of a wire is   per metre. It is bend in the form of a circle of diameter 2 m. A wire of the same material is connected across its diameter. The total resistance across its diameter AB will be

(a)

(b)

(c) 0.88

(d) 14π