You are watching: The resistivity of a wire depends on
|Picture 2.2 The high conductivity that copper renders it perfect for this electrode holder i beg your pardon carries huge currents to a stole making arc furnace.|
When we say the copper is a heavier steel than aluminium, we room comparing their densities. In a similar way, as soon as we say the copper is a better conductor than aluminium, we space comparing your resistivities.
Density and resistivity room both bulk properties the a material. Their value doesn\"t count on the size or shape of a particular sample only on the product itself.
Resistivity: relies on the product onlyResistance: counts on size and shape - and also on the material.
|What is resistivity?|
|In effect, the resistivity to represent the resistance across two opposite faces of a cubic metre of product (in the same way that density is the mass of a cubic metre). Resistivity tells just how resistive a material is.|
Resistivity has actually the symbol r - (rho come rhyme v snow) and its units room ohm metres.
|Picture 2.2 Graph that resistivities of some metals.|
|Table 3 shows some resistivities. Girlfriend will watch that resistivity different from around 10-8Wm to much more than 1016Wm more than 24 order of magnitude. No various other property of materials varies over such a wide range.|
|Picture 2.3 Graphics come illustrate how resistance varies through l, A and also rho.|
|To calculate the resistance R the a wire, we require to recognize three things:its length |
the longer the wire, the greater its resistanceits cross-sectional area Athe greater the area, the less its resistancethe resistivity that the material r the higher the resistivity, the higher its resistance.
resistance = resistivity × size / area
This equation specifies resistivity. We can rearrange it to gain a formula for resistivity:
resistivity = resistance × area / size
|a) Look at the electrode holder in the photograph at the top of the page. Use the table to to compare the resistivities that copper and also steel; usage this to describe why utilizing copper is an energy-efficient choice.|
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b) A wire made of a copper alloy is 5m in length and also has a cross-sectional area 1mm2. The resistance is 0.15W. Calculation the resistivity of this alloy.