# Plotting the wave forms of i(t), Vo(t) and Vi(t) when given charge vs time graph

Discussion in 'Homework Help' started by jamescolt, Sep 20, 2010.

Sep 19, 2010
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2. ### Georacer Moderator

Nov 25, 2009
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In your circuit, a great length of wire is depicted. Does the problem state its resistivity (specific electrical resistance)?

P.S. Please use the built-in picture attach tool that the forum provides. It gives better accessibility to the images.

3. ### jamescolt Thread Starter New Member

Sep 19, 2010
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Oh yes there is, I forgot to add the info.

In Figure 1, the voltage vi(t) is transferred to the load through a 100-ft copper transmission line. The diameter of the transmission line is 0.032 cm and its resistivity at 20 ⁰C is 1.723 μΩ.cm. Figure 2 shows one period of the electrical charge passing through this line. Neglecting the temperature effect.

I got about 6.5 Ohms as the resistance.

Oh sorry, will do next time.

4. ### Georacer Moderator

Nov 25, 2009
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The first step is to calculate the resistance of the line (the long cable). After that the rest is just formulas:

$i(t)=V_i(t)/R_{tot} \\
and\ V_o(t)=i(t) \cdot R \\
where\ R_{tot}=R+R_{line}$

Is that clear?

Last edited: Sep 20, 2010
5. ### jamescolt Thread Starter New Member

Sep 19, 2010
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Yeah now it is. Thaanks a lot.