The first law of thermodynamics The work of Joule and others may be summed up in a statement known as the first law of thermodynamics: Change in internal energy of any system = heat inflow + work done on the system or, in symbols U = Q + W (see page 78) This is simply a way […]
Importance of Joule’s work When an account of Joule’s work became known in the middle of the nineteenth century it aroused but little interest, as the concept of work and energy was new to science. At the time it was not generally realized that Joule’s experiments provided the first reliable experimental evidence for the truth of the […]
Temperature rise resulting from compression Anyone who has pumped up a bicycle tyre knows that the lower part of the pump barrel may become quite warm. Erroneously, this is often attributed to work done against friction. On reflection, however, one must come to the conclusion that the friction of an oiled plunger against the smooth barrel wall is […]
To measure the specific heat capacity of lead by the shot-tube method Whilst, as its name implies, the term specific heat capacity is used in internal energy calculations where the energy transfer is by heat, it is also used when the energy transfer is by mechanical means, i.e., by doing work on a body. The experiment we […]
Cheat calculations 1.How many Joules of”heat are given out when a piece ofiron of”mass 50 g and specific v’fieat capacity 460 J/kg K, cools front 80 C to 20 C? To say that the specific heat capacity of iron is 460 J/kg K means that 1 kg of iron gives out or takes in, as the case may […]
Specific heat capacity If we take equal masses of water and oil and warm them in separate beakers by the same gas burner it is found that the oil temperature may rise by 10 K in 3 min, but the water may rise by only 5 K. Since the rate of supply of heat is the same […]
Heat capacity The heat capacity of a body of any kind is defined as the heat required to raise its temperature by 1K. The SI unit of heat capacity is therefore the joule per kelvin (J/K). For the meaning and use of the kelvin in SI units and definitions see page 162.
Measurement of heat and internal energy We shall now deal with some of the calculations involved in heat and internal energy measurements. Since heat is a form of energy transfer, it is measured in joules the same as any other kind of energy. Now, the easiest way to produce heat, and at the same time be able […]
Potential energy transferred to internal energy in a waterfall From the results of his experiments, Joule came to the conclusion that the water at the bottom of a waterfall ought to be slightly warmer than that at the top. At the top of the fall the water possesses potential energy, which becomes transferred to kinetic energy as it […]
Joule’s experiments James Joule was the son of a Sale ford brewer and became interested in the subject of energy at a very early age. He spent many years making careful experiments to show that mechanical and electrical energy could be transferred to internal energy in water which produced a rise in temperature. His best-known apparatus is illustrated […]