An electric water kettle rated 2.1 kW is filled with 1.5 kg of water at 20°C. How many seconds does it take to reache boiling point of water ? Assume that there are no heat losses from the kettle. Specific heat capacity of water is 4200 Jkg^-1 K^-1 . 

• 60

• 120

• 240

• 480

An immersion heater with electrical resistance 7 Ω is immersed in 0.1 kg of water at 20°C for 3 min. If the flow of current is 4 A, what is the final temperature of the water in ideal conditions ? (Specific heat capacity of water = 4.2x 10³ Jkg^-1 K^-1)

• 28°C

• 48°C

• 52°C

• 68°C

Heat produced (cals) in a resistance R when a current I amperes flows through it for t seconds is given by the expression

• $\frac{{\mathrm{I}}^2\mathrm{Rt}}{4.2}$

• $\frac{{\mathrm{IR}}^2\mathrm{t}}{4.2}$

• $\frac{4.2 \mathrm{IR}}{{\mathrm{t}}^2}$

• $\frac{{\mathrm{IRt}}^2}{4.2}$

The temperature of equal masses of three different liquids A, Band Care 12°C, 19°C and 28°C respectively. The temperature when A and B are mixed is 16°C and when B and C are mixed is 23°C. The temperature when A and C are mixed is

• 18.2°C

• 22°C

• 20.2°C

• 24.2°C

A 10 Ω electric heater operates on a 110 V line. The rate at which heat is developed in watts is 

• 1310 W

• 670 W

• 810 W

• 1210 W

For a certain thermocouple, if the temperature of the cold junction is 0°C, the neutral temperature and inversion temperatures are 285°C and 570°C respectively. If the cold junction is brought to 10°C, then the new neutral and inversion temperatures are respectively

• 285°C and 560°C

• 285°C and 570°C

• 295°C and 560°C

• 275°C and 560°C

In which of the following substances does resistance decrease with increase in temperature ?

• Copper

• Carbon

• Constantan

• Silver

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