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Electricity

Blazing goIITian

Joined:	3 Nov 2008
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7 Apr 2009 18:27:46 IST

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challenging one - equalant resistance

None

resistance of each side is r then equalant resistance between A and B

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Madmax

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Joined: 24 Dec 2007

Posts: 1111

7 Apr 2009 18:36:21 IST

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3R/5

I dunno how Anshul (post below) has gotten 5/2R.....(His logic is correct....current thru the 2 branches EC and FD is zero)

Anshul Rai

Scorching goIITian

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7 Apr 2009 18:48:11 IST

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I think equivalent resistance is 5r/2. (no current through EC and FD)

Karan Singh

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7 Apr 2009 19:13:20 IST

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PD acrross F and D ; E and C are equal as current flow is equal for both due to symetry. So no current flows thru EC and FD.

so now

R(AB) = r

R(AFEB) = 3r

R(ADCB) = 3r.

All 3 are in parallel.

so R(eq) = ( 1/r + 1/3r + 1/3r )^(-1) = 3r/5.

so eq res = 3*r/5.

XYZ

Hot goIITian

Joined: 18 Jan 2009

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7 Apr 2009 19:15:39 IST

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The answer is 3r/5 only.

F and D are at the same potential.

E and C are at the same potential.

Now the equivalent resistance can be calculated easily.

Amitabh Anand

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Joined: 18 Feb 2009

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7 Apr 2009 19:24:15 IST

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D,F have same potential

C,E have same potential.

Noe remove the respective wires.

U have a parallel connection of 3r , r, 3r

Equivalent resistance=3r/5

Anshul Rai

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Joined: 9 Nov 2008

Posts: 271

8 Apr 2009 12:43:24 IST

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Oh! What a big calculation mistake I made! Answer should be (2/3r + 1/r)^(-1) = 3r/5. Sorry!

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