Exam 5: Heat, and D.C Circuits

When resistors of 2 Ω and 4 Ω are connected in parallel, their combined conductance is:

Decide whether each of these statements is True (T) or False For a moving coil meter of resistance R: (i) The current range of the meter can be increased by connecting a higher resistance than R in parallel. (ii) The voltage range of the meter can be increased by connecting a higher resistance than R in series.

Decide whether each of these statements is True (T) or False The specific heat capacity of water is 4200 J kg-1 K-1 and the specific latent heat of vaporisation of water at 100ºC is 335 kJ/kg. (i) It takes more heat to vaporise 1 kg of water at 100ºC than to heat it from 0ºC to 100ºC. (ii) To take 1 kg of water from liquid at 0ºC to vapour at 100ºC requires 339.2 kJ.

Two lengths X and Y of wire of the same material are in an electrical circuit. If wire X has twice the diameter of wire Y and is twice the length, the resistance of X is:

Decide whether each of these statements is True (T) or False For resistors of resistances 10Ω✡ and 5 Ω: (i) The combined resistance when they are connected in series is 15 Ω. (ii) The combined resistance when they are connected in parallel is 3.3 Ω.

Decide whether each of these statements is True (T) or False For an ideal gas: (i) Doubling the volume, with no change in temperature, doubles the pressure. (ii) Doubling the temperature on the Kelvin scale, with no change in volume, doubles the pressure.

Decide whether each of these statements is True (T) or False Copper has a linear coefficient of expansion of 0.000 017 /K and aluminium a linear coefficient of expansion of 0.000 023 /K. (i) With equal length copper and aluminium wires exposed to the same increase in temperature, the aluminium will increase in length more than the copper. (ii) To give the same increase in length for copper and aluminium wires for the same increase in temperature, the copper wire will need to be 1.35 time

Decide whether each of these statements is True (T) or False According to the kinetic model of an ideal gas: (i) The higher the temperature the larger the mean kinetic energies of the molecules. (ii) Increasing the volume occupied by the gas, with no change in temperature, results in the number of molecular collisions per second with the walls decreasing.