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If you need to know more about resistivity, you’ve come to the right place. On this blog post, we will analyze how different materials are resistant to electricity. We'll cover both their relative resistivity and conductivity, as well as what affects these properties. This way you'll be able to make an informed decision on the best material for your next project or invention. What is resistivity? In its most basic form, resistivity describes how a material resists the flow of electricity through it. The unit of measurement for resistivity is the ohm-metre (Ω·m) or ohm-centimetre (Ω·cm). Conductivity, which is closely related to resistivity, describes how easily electrons pass through a material (electrical conductors are examples of materials with high conductance). The unit for conductance is the siemens (S). Let’s work through an example to see how all this works in practice. Take an electrical current that travels one meter through a gold wire that has a resistance of 10 Ω. The current I flowing through the wire is 10 mA. If a piece of paper is placed in the path of the current, it conducts electricity as well as gold. In this case, the actual length of the paper represents R and the resistance R equals 10 Ω. The length of paper that conducts electricity is L = L = y I − y = 10 mA − x Ω L = 2x Ω Figure 1: Gold wire with a resistance of 10 Ohm and a piece of paper at its end. The amount by which the resistance R changes because of a change in length, or "L", is called resistivity, written as ohms per meter (Ω/m). The resistivity of copper is extremely high, around 106 Ω/m. Since the resistivity of copper increases as the temperature increases, electric current can flow through copper much more easily at higher temperatures. Copper wire has a resistance of about 4 Ω/m at room temperature. Before electric current was invented, people used all kinds of materials to make wires for direct current (DC). These were not very good conductors. The only materials that offered practical conductivity were metals such as silver or gold that had been heavily alloyed with other metals. Electrical conductivity of alloyed metals is usually around 30% higher than the original metal. If you make a wire out of this material, you don't have to worry about resistance, because the metal has added resistance. This is not the case with alternating current (AC) that requires careful handling of high voltage power sources. The higher the temperature, the lower the electrical resistance. This is because conductivity increases with temperature because electrons are moving faster in warmer materials. Resistivity vs Conductivity Let's look at some more examples of conductors and non-conductors. Silver wires have a negligible amount of resistivity, so they are simple models for how resistive materials behave in an electrical circuit. cfa1e77820
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