Tricky but interesting circuit problem ?

Find the voltage across terminals a and b, Vab

A) V/5

A) 4V/5

A) 2V/3

A) 3V/2

A) other

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3 Answers

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  • Anonymous
    1 month ago

    2R is by-passed

    Req = 4R // 4R = 2R

    Vab = V*Req/(Req+R) = V*2/(2+1) = 2V/3

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  • 1 month ago

    Without thinking, I would say answer A) is correct ;-)

    RealPro gave the full analyses. The trick is to spot the short circuited resistor (2R). 

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  • 1 month ago

    You ignore the 2R resistor because the current bypasses it through the leftmost wire. Resistance between A and B is (R+3R=4R) parallel to 4R which is 2R in total.

    The resistance of the whole circuit is 3R.

    2/3 of the circuit resistance is between A and B so 2V/3.

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