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**Efield in Composite Wire..Pls help!!**

**1. Homework Statement**

A 2.0m length of wire is made by welding the end of a 1.2m long silver wire to the end of an 0.8m long copper wire. Each piece of wire is 0.60mm in diameter. The wire is at room temperature. A potential difference of 5.0V is maintained between the ends of the 2.0m composite wire. What is the magnitude of E in the copper?

**2. Homework Equations**

E='roe'J , 'roe' is resistivity

J=I/A, A is cross sectional area

I= 45amperes

A= 2.827*10^-7 sqm

Resistivity of copper= 1.72*10^-8

Resistivity of silver= 1.47*10^-8

**3. The Attempt at a Solution**

I tried to calculate J first by substituting in values of I and A using the formula J=I/A and multiplying by 'roe'_copper but i still cant get the right answer!! I would like to ask the concept behind the E of a composite wire too..