Finding values from two equations

A transmission line is designed so it has self inductance, L = 7.0x10^-7 Hm^-1 & signal speed 70% of c 9speed of light)

Find characteristic impedance

**Now**

Z = √L/C (where C is capacitance, but shouldn't really matter just for the maths bit)

also

v = 1/ √LC

remembering

**L = 7.0x10^-7 Hm^-1**

v = 0.7c (c = 3x10^8 ms^-1)

7(3x10^8)/10 = 1/√7.0x10^-7 * C

so

C = √((10(7.0x10^-7))/(7*3x10^8))

C = √ 3.33x10^-15

**C = 5.77x10^-8 F**

Z = √L/C

Z = √7.0x10^-7/5.77x10^-8

**Z = 3.4 Ω**

Which isn't in the park as far as expected result goes, so AGAIN, please could you show me where I went wrong.

__________________

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Re: Finding values from two equations

Quote:

Originally Posted by

**froodles01** A transmission line is designed so it has self inductance, L = 7.0x10^-7 Hm^-1 & signal speed 70% of c 9speed of light)

Find characteristic impedance

**Now**

Z = √

**(**L/C

**)** (where C is capacitance, but shouldn't really matter just for the maths bit)

also

v = 1/ √LC

remembering

**L = 7.0x10^-7 Hm^-1**

v = 0.7c (c = 3x10^8 ms^-1)

7(3x10^8)/10 = 1/√

**(**7.0x10^-7 * C

**)**
so

C = √((10(7.0x10^-7))/(7*3x10^8))

C = √ 3.33x10^-15

**C = 5.77x10^-8 F**
Z = √L/C

Z = √7.0x10^-7/5.77x10^-8

**Z = 3.4 Ω**
Which isn't in the park as far as expected result goes, so AGAIN, please could you show me where I went wrong.

__________________

Just trying to keep up.

http://mathhelpforum.com/images/smilies/uhh.gif

As far as I understand your calculations:

1. You've forgotten to use parantheses (added in red)

2. To get the value of C you have to square both sides of the equation first.

Re: Finding values from two equations

A fresh pair of eyes has it every time.

Thanks. X