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De aan de schakeling toegevoerde stroom It is 84 mA.
Hoe groot is de stroom door R?

a   21 mA
b   36 mA
c   48 mA
d   63 mA

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Rv23 = 5Ω

Rv123 = 5 + 10 = 15Ω

Rv45 = 10 + 10 = 20Ω

Rt is 15 + 20 parallel
Rt n= 1/ (1/15 + 1/20) = 8.5 Ω

Ut = It x Rt = 84 mA x 8.5 = 0.714 V

IR123 = Ut / Rv123 =
IIR123 = 0.714  / 15 =  0.0476 A = 48 mA

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