Resistivity Measurement, Resistors and Ohm’s Law

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Resistivity Measurement, Resistors and Ohm’s Law | For various materials, we may study their characteristics in different aspects, including chemical properties, physical properties, mechanical properties and electrical properties. In this experiment, the student is expected to study the major electrical properties of some common materials. Basically, the resistivity is a common parameter to measure how conductive the material is. Generally, the conductive material has a very low resistance of (mΩ) order. On the contrary, an insulating material has a very high resistance of tens of (MΩ). By definition, the resistivity of a conductor is given as below:

The most fundamental relationship of circuit theory is Ohm’s law. Ohm’s states that in a purely resistive circuit, current is directly proportional to voltage and inversely proportional to the resistance. There are three ways to express Ohm’s Law, namely,

Small resistors, the kind that you encounter most often in electronic products, are too small to have their values printed on the components. Instead, these smaller resistors are usually covered by an epoxy or similar insulating coating over which several colored bands are printed radially as shown in Figure 1.

The first two bands represent the first and second digits of the resistance values. The third band is called the multiplier band and represent the number of zeros following the first two digits; it is usually given as the power of ten. The fourth band indicates the tolerance of the resistor, and the fifth band (if present) is an indication of the expected reliability of the components. Figure 2 lists the colors of the various band and the corresponding values. Download free Resistivity Measurement, Resistors and Ohm’s Law.pdf here

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