An airplane black box contains a bunch of unknown resistances and batteries con- nected in unknown way such that (1) a 9 Ohm resistor across

Question

An airplane black box contains a bunch of unknown resistances and batteries con- nected in unknown way such that (1) a 9 Ohm resistor across the terminals of the circuit box draws 0.80 A, and (2) an 17 Ohm resistor draws 0.50 A. What resistance will draw 0.12 A

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Nguyệt Ánh 4 years 2021-08-24T12:31:50+00:00 1 Answers 6 views 0

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  1. Xavia
    0
    2021-08-24T12:32:55+00:00
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    Answer:

    The unknown resistance which will draw a current of 0.12 A is 84.5 ohm

    Explanation:

    Let say the emf of the cell is E and internal resistance of the system is “r”

    now we will have

    E = (r + R) i

    here we have 9 ohm resistance draw current of 0.80 A

    E = (9 + r)(0.80)

    also we know that 17 ohm resistance will draw current of 0.50 A

    E = (17 + r)(0.50)

    so we will have

    8.5 + 0.50 r = 7.2 + 0.80 r

    0.30 r = 1.3

    r = 4.33 ohm

    also we have

    E = 10.67 V

    now when 0.12 A current is drawn across unknown resistance then we have

    10.67 = (R + 4.33)(0.12)

    so we have

    R = 84.5 ohm

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