Circuit Problem. What is the unknown resistance R?

Question

http://img253.imageshack.us/img253/4656/pysis0.png

In the circuit of figure, the 5.0Ω resistor is removed and replaced by a resistor of unknown resistance R. When this is done, an ideal voltmeter connected across the points b and c reads 1.9 V

Find

a. the current in the circuit.

b. the resistance R.

Answer 1

a. current = .7625 amps

b. R= 2.492 ohms

Answer 2

current is I = E/R = 1.9 / 9 = 0.211 amps.

Voltage drops across the 1.6 and 1.4 (total 3 ohms) total

E= 0.211 x 3 = 0.633 volts

Adding around the loop,

V5 = 16-8-1.9-0.633 = 5.467

R5 = 5.467/0.211 = 25.91 ohms

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