End of Topic Exam 1, quarter 3

When a thermocouple has one junction in melting ice and the other junction in boiling water it produces an e.m.f. of 63 μV. When the second junction is placed in a cup of coffee, the e.m.f. produced is 43 μV. Calculate the

temperature of the coffee.

• 71°C

• 64°C

• 75°C

• 68°C

• The correct answer is not shown

A 500 W kettle contains 300 g of water at 20°C. Calculate the minimum time it would take to raise the temperature of the water to 80°C.

• 188 s

• 176 s

• 163 s

• 151 s

• The correct answer is not shown

The figure shows the apparatus used to measure the specific latent heat of the sublimation of carbon dioxide. The change in mass of the solid carbon dioxide in a time interval of 5 minutes is measured with the heater switched off . The change of mass, in the same time interval, is found with the heater switched on. The energy to supplied to the heater is also measured. The results are shown in the table.

Find the specific latent heat of sublimation of carbon dioxide

• 619 J/g

• 652 J/g

• 690 J/g

• 588 J/g

• The correct answer is not shown

The specific latent heat of sublimation is

• greater than either the specific latent heat of fusion or the

  specific latent heat of vaporisation.

• greater than the specific latent heat of fusion but less than the

  specific latent heat of vaporisation.

• greater than the specific latent heat of vaporisation but less than the

  specific latent heat of fusion.

• less than either the specific latent heat of fusion or the specific latent heat of vaporisation.

• The correct answer is not shown

The change in mass of the nitrogen is measured over a specific time interval with the heater switched off . The heater is switched on, transferring energy at 40 W, and the change of mass is found once more.

The results are shown in the table.

Calculate the specific latent heat of vaporisation of liquid nitrogen.

• 205 J/g

• 214 J/g

• 224 J/g

• 235 J/g

• The correct answer is not shown

A cylinder holds 140 dm³ of nitrogen at room temperature and pressure. Moving slowly so that there is no change in temperature, a piston is pushed to reduce the volume of the nitrogen to 56 dm³. Calculate the pressure of the nitrogen aft er compression.

• 2.5 × 10⁵ Pa

• 4.0 × 10⁵ Pa

• 5.0 × 10⁵ Pa

• 2.3 × 10⁵ Pa

• The correct answer is not shown

A vessel of volume 200 dm³ contains 3.0 × 10²⁶ molecules of gas at a temperature of 107°C. Calculate the pressure exerted by the gas on the vessel walls.

• 6.2 × 10⁶ Pa

• 6.6 × 10⁶ Pa

• 7.3 × 10⁶ Pa

• 7.9 × 10⁶ Pa

• The correct answer is not shown

The density of air at 30°C and pressure 1.0 × 10⁵ Pa is 1.21 kg m⁻³.

Calculate the average speed of air molecules.

• 500 m/s

• 520 m/s

• 550 m/s

• 570 m/s

• The correct answer is not shown

The value in amps of an alternating current is represented by the equation

I = 2 sin (60πt).

What time t where the current I is equal to I_rms

• 4.2 x 10^-3 s

• 6.3 x 10^-3 s

• 3.6 x 10^-3 s

• 8.3 x 10^-3 s

• The correct answer is not shown

The a.c. mains of 240 V r.m.s. is connected to the primary coil of a transformer, which contains 2500 turns. The r.m.s. output of the transformer is 6.0 V.

Calculate the number of turns on the secondary coil.

• 25

• 38

• 19

• 63