- #1

m_physics

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**1.Problem**

A current of 0.76A flows through a copper wire 0.44mm in diameter when it is connected to a potential difference of 15V. How long is the wire?

A current of 0.76A flows through a copper wire 0.44mm in diameter when it is connected to a potential difference of 15V. How long is the wire?

**2. Homework Equations (Missing any?)**

V=IR

R=row(L/A)

A=pieD^2/4

row=resistivity=p

p of copper=1.72 x 10^-8

V=IR

R=row(L/A)

A=pieD^2/4

row=resistivity=p

p of copper=1.72 x 10^-8

**3.Attempt**

Pretty sure conversion is wrong.

**V=IR**

15=(.76a)R

R=19.737

D=.44mm

**mm to m**

4.4 x 10^-5m

**A=pieD^2/4**

A=(3.14)(4.4 x 10^-5)^2/4

A=1.512 x 10^-9

Plug back into the resistance equation for L

**R=row(L/A)R=row**

19.737=(1.72 x 10^-8)(L/1.512 x 10^-9)

2.999x10^-8=1.72 x 10^-8L

L=(2.999x10^-80)/(1.72 x 10^-8)

**L=1.744m**

**Correct Answer: 170m**