21.

Six molecules speeds 2 unit, 5 unit, 3 unit, 6 units, 3 unit and 5 unit respectively. The rms speed is

• 4 unit

• 1.7 unit

• 4.2 unit

• 5 unit

Which one of the figure gives the temperature dependence of density of water correctly ?

A piece of wood is floating in water. When the temperature of water rises, the apparent weight of the wood will

• increase

• decrease

• may increase or decrease

• remain same

An experiment takes 10 min to raise temperature of water from 0°C and 100°C and another 55 min to convert it totally into steam by a stabilized heater. The latent heat of vaporization comes out to be

• 530 cal/g

• 540 cal/g

• 550 cal/g

• 560 cal/g

Which of the following substance has the highest elasticity ?

• Steel

• Copper

• Rubber

• Sponge

A wire is stretched under a force. If the wire suddenly snaps the temperature of the wire

• remains the same

• decrease

• increase

• first decrease then increase

When the room temperature becomes equal to the dew point, the relative humidity of the room is

• 100 %

• zero %

• 70 %

• 85 %

At what temperature will the rms speed of air molecules be double that NTP ?

• 519° C

• 619° C

• 719° C

• 819° C

4 point charges each +q is placed on the circumference of a circle of diameter 2d in such a way that they form a square. The potential at the centre is

• 0

• $\frac{4\mathrm{q}}{\mathrm{d}}$

• $\frac{4\mathrm{d}}{\mathrm{q}}$

• $\frac{\mathrm{q}}{4\mathrm{d}}$

64 identical spheres of charge q and capacitance C each are combined to form a large sphere. The charge and  capacitance of the large sphere is

• 64q, C

• 16q, 4C

• 64q, 4C

• 16q, 64C