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Name: Jason
Status: other
Age: 20s
Location: N/A
Country: N/A
Date: 2000-2001


Question:
May I know how do I calculate the amount of heat generated given the amount of current(I) passing through a length(L)of copper wire of a certain width(W)?


Replies:
Power is energy/unit time and energy is the equivalent of heat. The power of and electrical resistor is current x voltage or current x current x resistance.

The electrical resistance is resistivity x length of wire/cross sectional area.

I don't have the resistivity of copper at my finger tips, but it is available through various hand books. Hence the Heat=Power x Unit Time= (Current x Current x resistivity x length of wire)/cross sectional area.

Dr. Myron


Assuming the material you are dealing with is ohmic, you find the resistance by:

R = rho L/A

R is the resistance.

rho is the constant of resistivity associated with the material, and is available in standard tables.

L is the length.

A is the cross sectional area.

Q = I^2 Rt

Q is for the energy exchange from electrical potential energy into thermal energy.

I is the current.

R is the resistance.

t is for the amount of time the current is flowing.

This information is available in any standard introductory college text containing electricity.

---Nathan A. Unterman


Heat generated per unit time (i.e., power, as in Watts per second) is given by P=V I=R I^2 where V is the voltage across the wire, R is the wire resistance, and I is the current. Note that current and voltage are related by V= R I.

The resistance of a copper wire of length L and cross-sectional area A (which must be known) is given by R= (r L)/A where r is the electrical resistively of copper. Electrical resistively of metals are listed in text books.

As you can see, you need two of the three items (R, I, V) to evaluate the power. If you know V and I, you do not need to calculate R (use P=V I). If only V or I is known, then evaluate R as in paragraph 2.

AK

Dr. Ali Khounsary



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