31.

The manifestation of band structure in solids is due to

• Heisenberg's uncertainly principle

• Pauli's exclusion principle

• Bob's correspondence principle

• Boltzmann's law

If there were no gravity, which of the following will not be there for a fluid ?

• Viscosity

• Surface tension

• Pressure

• Archimedes' upward thrust

For the stationary wave

      $\mathrm{y} = \mathrm{u} \sin \left(\frac{\mathrm{\pi x}}{15}\right) \cos 96\mathrm{\pi t}$

The distance between a node and the next antinode is

• 7.5 cm

• 15 cm

• 22.5 cm

• 30 cm

An electric heater of resistance 6 Ω works for 10 min on a 60 V line. The energy liberated in this period of time is

• 7.2 × 10³ J

• 3.6 × 10⁵ J

• 43.2 × 10⁴ J

• 28.8 × 10⁴ J

A circular coil has 500 turn of wire and its radius is 5 cm. The self inductance of the coil is

• 25 x 10^-3 mH

• 25 mH

• 50 x 10^-3 H

• 50 x 10^-3 mH

The unit of inductance is

• $\frac{\mathrm{volt}}{\mathrm{ampere}}$

• $\frac{\mathrm{joule}}{\mathrm{ampere}}$

• $\frac{\mathrm{volt}-\mathrm{second}}{\mathrm{ampere}}$

• $\frac{\mathrm{volt}-\mathrm{ampere}}{\mathrm{second}}$

The diameter of each plate of an air capacitor is 4 cm. To make the capacity of this plate capacitor equal to that of 20 cm diameter sphere, the distance between the plates will be

• 4 × 10^-3 m

• 1 × 10^-3 m

• 1 cm

• 1 × 10^-3 cm

The electric potential V is given as a function of distance x (m) by V = (5x² + 10x − 9) volt. Value of electric field at x=l m is

• 20 V/m

• 6 V/m

• 11 V/m

• − 23 V/m

Which one of the following is ferromagnetic?

• Gold

• Wood

• Manganese

• Nickle

Shown below is a distribution of charges. The flux of electric field due to these charges through the surface is

• $\frac{3\mathrm{q}}{{\mathrm{\epsilon }}_0}$

• zero

• $\frac{2\mathrm{q}}{{\mathrm{\epsilon }}_0}$

• $\frac{\mathrm{q}}{{\mathrm{\epsilon }}_0}$