How to Calculate the Resistance of Metallic Cables?
In basic engineering circuit analysis it sometimes becomes very important to know the resistance of a conductor, for example the mains cable. Let's see how it's calculated:
Resistance of Metallic Conductors: It may be calculated using the following simple formula:
R = ρ×l/a
where R = Resistance in Ohms, ρ = Resistivity of the conductor material, l = Length of the conductor and a = cross sectional area of the conductor.
The resistivity of the material is actually the resistance present in a meter long conductor having a cross sectional area of 1mm2 and is constant.
Electrical Power: Its unit is Watt and is defined as the product of current and voltage.
Hence W = IU = I2R, (by replacing U = IR).
The following given problem and its solution will help us to understand the use of the above discussed two electrical parameters:
Q: Referring to the adjoining figure, an electrical heater consuming 6 amperes of current is connected to a 220 volts supply by a copper cable having a length of 12 meters and a diameter of 1.5 mm2. Calculate the resistance of the cable and also the power consumption of the appliance. (ρ of copper is 0.017 Ωm).
A: First let’s find out the resistance of the conductor i.e. the cable as:
R = ρ×l/a = 0.017 × 12/1.5 = 0.136, since the cable is made up of two wires, multiplying the result by 2 we get the final result as 0.272 Ohms.
The Power of the heater can be easily obtained in the following manner:
P = I × U = 6 × 220 = 1320 Watts.
Through the above explanations we have perhaps just been able to scratch the surface and a comprehensive answer to the question “What is basic engineering circuit analysis?" can be so huge that it would fill volumes, however, hopefully you should be able to learn much more regarding this through my future articles.