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

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 reach the boiling point of water ? Assume that there are no heat losses from the kettle. Specific heat capacity of water is 4200 Jkg^-1K^-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 = 4.2 × 10³ Jkg^-1K^-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

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

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

• $\frac{4.2 \mathrm{IR}}{2}$

• $\frac{{\mathrm{IRt}}^2}{4.2}$

1 g of steam at 100°C and equal mass of ice at 0°C are mixed. The temperature of the mixture in steady state will be (latent heat of steam = 540 cal/g, latent heat of ice = 80 cal/g)

• 50°C

• 100°C

• 67°C

• 33°C

A steel scale is to be prepared such that the millimetre intervals are to be accurate within 6 x 10^-5 mm. The maximum temperature variation during the ruling of the millimetre marks is (α = 12 x 10^-6/° C) 

• 4.0° C

• 4.5° C

• 5.0° C

• 3° C

The unit of specific conductivity is

• Ω cm^-1

• Ω cm^-2

• Ω^-1 cm^-1

• Ω cm^-3

A bucket full of hot water is kept in a room. It cools from 75°C to 70°C in t₁ minutes, from 70°C to 65°C in t₂ minutes and from 65°C to 60°C in t₃ minutes. Then

• t₁ < t₂ < t₃

• t₁ = t₂ = t₃

• t₁ < t₂ > t₃

• t₁ > t₂ > t₃

Curie-Weiss law is obeyed by iron

• at Curie temperature only

• at all temperatures

• below Curie temperature

• above Curie temperature