To find the electrical resistance of the conductor, use the corresponding formulas. Resistance of the site of a chain is under the law of Ohm. If material and the geometrical sizes of the conductor is known, its resistance can be calculated by means of a special formula.
It is required to you
- - tester;
- - caliper;
- - ruler.
Instruction
1. To find resistance, use Ohm's law for subcircuit. It says that current on this site of a chain is directly proportional to voltage drop on it and is inversely proportional to resistance. Switch a tester for measurement of current and connect it in a chain consistently. Express value of current in amperes. Then, switch a tester for voltage measurement and attach it in parallel to the site of a chain. Take from the device readings of tension in volts. If current in a chain constant, attaching a tester, pay attention to that he joined a current source the poles of the same name. Calculate value of resistance, having divided tension into current: R=U/I. Receive result in Ohms.
2. If material is known and it is possible to measure the geometrical sizes of the conductor, calculate its resistance by means of other formula. For this purpose find the specific resistance of the conductor in the special table. It has to be measured in Ohm • mm²/м in order that cross-sectional area could be measured in mm².
3. Measure the cross-sectional area of the conductor. For this purpose measure by a caliper its diameter in millimeters, square it, and then increase this value by 3.14 and divide into 4:S=3.14•d²/4. Cross-sectional area will turn out in mm².
4. By means of a ruler or a roulette measure length of the conductor which resistance needs to be found. Express length in meters. Find resistance of the conductor, having increased its specific resistance by its length and having divided into R=ρcross-sectional area \• l/S.
5. It is possible to measure resistance of the conductor or the site of a chain, without making any calculations. For this purpose it is necessary to switch a tester to an ohmmeter operating mode. To make sure that the site of a chain is disconnected from a current source, then in parallel to attach a tester to it. It will show resistance of this site of a chain.