To find tension at the known value of current, determine additional parameter. This resistance of the site of a chain on which tension is measured. If it is unknown, determine it by a formula, having measured length and section of the conductor on the site. If resistance of the consumer is unknown, and power is known, calculate tension on it by the corresponding formula.
It is required to you
- - tester;
- - table of specific resistance
Instruction
1. Determination of tension on current and resistance. Measure resistance of the site of a chain if it is not known in advance, having attached to it a tester with the corresponding settings. Attach the device parallel to the conductor at the opened chain. Recustomize a tester for measurement of current (in the ampermeter mode). Include it in a chain consistently and measure value of current.
2. Using the law of Ohm (current on the site of a chain is directly proportional tension and is inversely proportional to resistance), find value of tension. For this purpose increase current by resistance of the site of a chain (U=I•R).
3. If there is no device for measurement of resistance, define material of which the conductor on the site of a chain is made, and find its specific resistance according to the corresponding table. Find also length and section of a wire. Then tension will be equal to the work of current on the specific resistance and the cross-sectional area of the conductor divided into its length by U=I • ρ\• S/l. It is possible to check result of calculations, having attached a tester in the voltmeter mode in parallel to the site of a chain.
4. Determination of tension on device power. Attentively examine the case of the device or study its technical data sheet. There the power consumed by this device will be surely specified. If it was not succeeded to find such data, measure the power consumed by the studied consumer, in a different way.
5. For determination of power attach a tester in the wattmeter mode in parallel to the working device. On its screen the value of the power consumed by the device will appear. You perform measurement in watts. To define value of tension on the device, divide the found power into current in amperes (U=P/I). The result will be received in volts.