# Magnetostatic Problems

1. Sep 15, 2004

### kelvintc

1) Calculate the self-inductance of a coaxial cable of inner radius a and outer radius b. The inner conductor is made of an inhomogenous material having u = 2u0/(1+r)
Answer : u0L/8pie + u0L/pie (ln(b/a) - ln((1+b)/(1+a)))

2) Two #10 copper wires(2.588 mm in diameter) are placed parallel in air with a seperation distance d between them. If the inductance of each wire is 1.2uH/m, calculate
(a) L(in) and L(ext) per meter for each wire
(b) The seperation d
Answer : (a)0.05, 1.15 uH/m, (b) 40.79cm

3) A conductor of radius a is bent into a circular loop of mean radius r. If r = 10cm and 2a = 1cm, calculate the internal inductance of the loop.

Really can't the number 1 answer. I get a^3 in my answer. Number 2 no idea since L = L(in) + L(ext). As well as number 3.

Thank you.

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Last edited: Sep 16, 2004
2. Sep 16, 2004

### kelvintc

cannot use Latex code anymore?

3. Sep 16, 2004

### Tide

Apparently they changed servers and LaTeX broke but they're working on fixing it.

4. Sep 16, 2004

### kelvintc

anyone can help me on these magnetostatic problems? i'm stucked ..