Slide Wire Experiment

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Slide Wire Experiment (E-4)

This experiment was engaged upon by measuring the internal resistance of three power sources and the electromotive force (emf). The potential difference between the terminals of such a source, when no current flows to en external circuit, is called an electromotive force, or emf source. The three power sources were a new 1.5V hobby battery an old 1.5V hobby battery, and a Daniel cell. A seat or source if electromotive foce may be any device that converts one type of energy (chemical, mechanical, light, etc.) into electrical energy. The work required to move 1 unit of positive charge from the negative to the positive terminal of a seat of emf, defines electromotive force in terms of work the seat of emf doe on electrical charges.

All batteries, either new, old or Daniel cell, will give off some internal resistance. The internal resistance of the battery is due to its ability to hold back the total flow of charge from one electrode to another. The terminal voltage equals the emf when no current is drawn from the battery. This is determined by the chemical reactions in the battery. In the case of a dry or wet cell, the internal resistance depends on the construction of the cell, and the size and conditions of its electrodes. On the other hand, the emf is a characteristic of the chemical process in the cell or battery. A potentiometer was used in our experiment to make comparisons of an unknown emf, u, with the emf of a standard cell, u.
We assembled the apparatus as shown in figure 1 of the lab manual, connected the slide directly to the power supply set for 2V, kept it at standby until the measurements were achieved. Next, we calibrated the slide wire potentiometer with standard cell. Thus, we determined the distance x, on the slide wire and we recorded the value of x in Table 1. Then we measured the emf of a new 1.5V hobby battery, by connecting the new hobby battery and we determined the distance ...