Resistance In A Wire Coursework Evaluation

Resistance In A Wire Coursework Evaluation-33
Observe what happens to the steel wire after you connect the clip.

First, select a suitably low resistance specimen to use in this experiment.

I suggest the electromagnet coil specified in the last chapter or a spool of wire where both ends may be accessed.

A 6-volt “lantern” battery essentially short-circuited by a long piece of wire may produce currents of this magnitude, and your ammeter needs to be capable of measuring it without blowing a fuse or sustaining other damage.

Make sure the highest current range on the meter is at least 5 amps!

Very small resistances may be measured easily by using large current, providing a more easily measured voltage drop from which to infer resistance than if a small current were used.

Because only the voltage dropped by the unknown resistance is factored into the calculation—not the voltage dropped across the ammeter’s test leads or any other connecting wires carrying the main current—errors otherwise caused by these stray resistances are completely eliminated.A current is passed through the unknown resistance and measured.The voltage dropped across the resistance is measured by the voltmeter, and resistance calculated using Ohm’s Law (R=E/I).CROSS-REFERENCES Lessons In Electric Circuits, Volume 1, chapter 8: “DC Metering Circuits” LEARNING OBJECTIVES SCHEMATIC DIAGRAM ILLUSTRATION INSTRUCTIONS Although this experiment is best performed with two meters, and indeed is shown as such in the schematic diagram and illustration, one multimeter is sufficient.Most ohmmeters operate on the principle of applying a small voltage across an unknown resistance (R) and inferring resistance from the amount of current drawn by it.For experimenters on a budget, this may not be possible.Whatever ammeter is used should be capable measuring at least a few amps of current.The quotient will be equal to the specimen’s resistance in ohms.The new HTML5 sims can run on i Pads and Chromebooks, as well as PC, Mac, and Linux systems.Switch the meter to its voltage mode, connect it across the specimen’s connection points, and re-connect the battery, quickly noting the voltage indication.You don’t want to leave the battery connected to the specimen for any longer than necessary for obtaining meter measurements, as it will begin to rapidly discharge due to the high circuit current, thus compromising measurement accuracy when the meter is re-configured and the circuit closed once more for the next measurement.


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