The experimental setup ready for the measurement is shown in figure 1. From these measurements, a time dependence of kinetic energy, gravitational potential energy and electric energy that is dissipated as heat is determined, compared graphically and discussed with respect to energy conservation.
Freefall position graph series#
voltage drop on a series resistor) in the coil are recorded simultaneously.
The time dependence of the vertical position of the bar magnet as well as the induced current (i.e. A bar magnet is released from a certain height above the centre of the vertically oriented coil. The basic idea of the experiment is the following. A closer look at the conversion from mechanical to electric energy in the cases that involve magnetic fields can be found elsewhere. In our case the transformation of the mechanical work into electric energy is enabled by the magnetic field. In the following treatment the term electric energy will be used for electric potential energy.
Freefall position graph verification#
The second experiment enables verification of energy conservation with higher precision and is more suitable as a student laboratory experiment at introductory physics level. The first experiment deals with the time dependence of the energy balance and is particularly suitable as an interactive lecture demonstration. Two versions of the experiment are described. In the present paper, we describe simple experiments that allow one to demonstrate the conservation of energy where the initial gravitational potential energy is transformed into kinetic energy and electric potential energy, which in turn transforms into thermal energy. On the other hand, examples that show quantitatively the conservation of energy for a combination of mechanical and electric energy are rare. In the literature, one can find several reports on experiments that demonstrate or prove energy conservation in cases where mechanical energy is transformed from one form to another. This type of measurements can be part of the lectures or student laboratory activities. Such systems enable quantitative verification of energy conservation in real time. In this respect, computer-based data acquisition systems brought an important improvement in teaching physics. Stories like this are an important part of instruction, especially when the subject is abstract, but the ability to apply knowledge in new situations comes through the active engagement in concrete examples. Knowing the properties of the blocks (such as volume) she is also able to find the missing blocks. Once the mother realizes this law she is able to predict how many blocks have been added or hidden during the day when the child has been playing with them. The story illustrates the law of conservation of energy: whatever the child does with the blocks, the number of blocks remains the same. Perhaps the best illustration of the principle of energy conservation, described as a short story about a mother and a child whom she leaves alone in a room with 28 absolutely indestructible blocks, has been given by Feynman.
the formulation of the energy conservation law looks very simple, it is well known that it is one of the most problematic laws when required to be applied in various situations at primary and secondary school levels and also at higher level.
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