Thermal Heating The density of charge-carrying electrons in copper is 8.5 times

Question

Thermal Heating The density of charge-carrying electrons in copper is 8.5 times 1028 electrons m-3, its resistivity is 1.72 times 10-8 Ohm middot m, and the drift speed is 3.20 times 10-3 m/s. The wire has a diameter of 6.00 mm and a length of 1.00 m. At what rate must thermal energy be carried off by a cooling medium if the wire is to maintain its temperature? Tries 2/20 Previous Tries Thermal Heating The density of charge-carrying electrons in copper is 8.5 times 1028 electrons m-3, its resistivity is 1.72 times 10-8 Ohm middot m, and the drift speed is 1.00 times 10-3 m/s. The wire has a diameter of 5.95 mm and a length of 1.10 m. At what rate must thermal energy be carried off by a cooling medium if the wire is to maintain its temperature?

Explanation / Answer

i = nAvQ

n = 8.5*10^28

A ={pi*(6*10^-3)^2/4 }

v = 3.2*10^-3

Q = 1.6*10^-19 C

i= 1230.5 A

R = rho*l/A = 6.08*10^-4

E = I^2*R = 921.08 W

For second case

n is same

A = pi*(5.95*10^-3)^2/4

v=1*10^-3

Q is same

i = 378.148 A

R = rho*l/A = 6.80*10^-4 ohms

Power = i^2*R = 97.3 W

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