a) Calculate the ratio of the resistance of copper to that of carbon at the rais

Question

a) Calculate the ratio of the resistance of copper to that of carbon at the raised temperature. Coefficient of thermal expansion for copper is 0.00680C while for carbon -0.00050C.

Express your answer using two significant figures.

b) Assuming they have the same voltage across them, calculate the ratio of the current in the copper compared to the carbon at the raised temperature.

Express your answer using two significant figures.

c) Repeat part B. for the ratio of the power delivered.

Express your answer using two significant figures.

Explanation / Answer

here,

thermal conductivity of copper, dcu = 0.00680 celcius
thermal conductivity of carbon, dc = -0.00050 celcius

resistance is given as ,

R = d*L/A

where,
L = length
A = area
d = coefficient of thermal expansion,

Part A:
Rcu/Rc = dcu/dc
Rcu/Rc = 0.00680 / -0.00050
Rcu/Rc = - 13.6

Part B:
From Ohms's Law
I = V/R

as voltage remains same therefore,

Icu/Ic = Rc/Rcu
Icu/Ic = -1/(13.6)
Icu/Ic = - 0.0735

Part C:
Power = I^2*R , therefore writing in terms of copper and cabon

Pcu/Pc = (Icu/Ic)^2 * (Rcu/Rc)
Pcu/Pc = (- 0.0735)^2 * (- 13.6)
Pcu/Pc = -0.073

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