Each edge of an Icosidodecahedron is a 2 Ω resistor. Then find the effective resistance between any 2 adjacent vertices.
Round off your answer up to 2 decimal places.
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I got the problem wrong because of a really stupid mistake :( However I have the way to prove that formula using the principle of superposition: let A and B be two adiacent points. We will consider two configurations: 1) a current i=1A flows trough A: B will receive 1/4 A because there are 5 adjacent vertices to A. There are 29 vertices from which i will flow out: trough each of them flows 1/29A 2) a current i is "sucked" from B: there is still 1/4A which goes from A to B; from every vertex there is 1/29 A entering current.
Superimposing those two, the potential difference between A and B is 1/2 R i, while in the present configuration we have a 0 current in each vertex different from A and B, where flows i+i/29=30/29 i current through a resistance r, which corresponds to a potential V=R eff 30/29 i Equating the two potentials gives Reff=R*29/60. In this case R=2 ohm
The formula makes it a piece of cake . however i wasn't aware of it so i used kirchoff's laws .
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Perhaps it takes a lot of time, doesn't it?
Great!!! I just found this formula somewhere ,i tried to prove it but was unable to do so,but this result is pretty useful where you have to solve a lot of questions in a limited amount of time.
hey, tried it by using symmetry and still i'm getting wrong !, i'm getting 11/15 . help if u can !
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never mind, it's an Icosidodecahedron, I misread this.
Describe the icosidodecahedron. The 2 1 edgeweights are conductances and are the reciprocal of the 2 Ω resistances.
nvertices = PolyhedronData [ Icosidodecahedron , VertexCount ] ;
edges = Table [ e [ [ 1 ] ] ↔ e [ [ 2 ] ] , { e , PolyhedronData [ Icosidodecahedron , Edges ] } ] ;
g = PlanarGraph [ Range [ nvertices ] , edges , VertexLabels → Name , EdgeWeight → ConstantArray [ 2 1 , Length [ edges ] ] ] ;
The Wolfram Mathematica Mathematica algorithm that does the mesh analysis to compute all vertex to vertex effective resistances.
The PseudoInverse is the Moore-Penrose Inverse .
resistance = With [ { Γ = PseudoInverse [ With [ { wam = WeightedAdjacencyMatrix [ $#$1 ] } , DiagonalMatrix [ Tr /@ wam T ] − wam ] ] } , Outer [ Plus , Diagonal [ Γ ] , Diagonal [ Γ ] ] − Γ − Γ T ] & ;
The invocation of the algorithm above.
r = resistance ( g ) ;
The extraction of the effective resistance across all edges and a tally of the values present (the algorithm outputs resistance for conductance and vis-a-vis).
result = Tally [ Table [ r [ [ e [ [ 1 ] ] , e [ [ 2 ] ] ] ] , { e , edges } ] ] ⟹ ( 3 0 2 9 6 0 )
This result shows that, in fact, all the effective resistances across each edge are the same. Below are the numeric version of the values.
N [ result ] ⟹ ( 0 . 9 6 6 6 6 7 6 0 . )
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R = 2 ( v − 1 ) r / v . n where v is the number of edges of the figure, n is the number of edges meeting at point and finally r is the resistance of each edge. This formula works for any polyhedron.
Substituting these values we get R = ( 3 0 2 9 ) Ω = 0 . 9 7 ( Ω )