Circuits In Parallel Pt #2

Question

Two resistors r1=6Ohms and r2=12Ohms are connected in parallel to each other and in series to r3=2Ohms. An ammeter measure an electric current of 3 A flowing through resistor r3. What is the net voltage applied to the circuit?

Answer 1

The current I flowing through the parallel combination of r₁ and r₂ is the same as the current flowing through r₃. Find the equivalent resistance of the r₁ and r₂ combination, use Ohm's law to get the voltage across the the combination, use Ohm's law to get the voltage across r₃, and then add the voltages.

V = V₁₂ + V₃

V = Ir₁₂ + Ir₃

V = I[r₁r₂/(r₁ + r₂)] + Ir₃

Plug in the given values of r₁, r₂, r₃, and I, and get V in volts.