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Need Electrics Circuit Help

X

Xylitol

Diamond Member
Three resistors (R1 = 19 , R2 = 38 , and R3 = 10 ) are connected to a battery. R1 and R2 are connected in parallel and the R1/R2 network is connected in series with R3. The voltage across R1 is 3 V.

Is the question

Ohm's Law: V= R* I

1.5 = 38 * I
Solve for I = .039 right?

The site says that my asnwer is wrong
Can someone help me?
 
I'm pretty rusty. I'm not totally positive about the way I figured the current through each individual resistor, but anyway...

The total resistance of two resistors in parallel is (R1 * R2)/(R1 + R2), which in this case gives us 12.667. Voltage is common to resistors in parallel, so we can decide that the TOTAL current thru the two parallel resistors is 3/12.667 = 0.237. Current thru any particular resistor is proportional to its share of the load, so R2 would get half the current that R1 gets, so 1/3 * 0.237 = 0.079 (current thru R2), and 2/3 * 0.237 = 0.158 (current thru R1).

If I'm wrong, somebody please correct me.

 
Yea it makes sense now but my brain is dead at almost 3:00 and i cant find voltage...
I just plugin for Ohm's Law right?
 
Originally posted by: Garth
I'm pretty rusty. I'm not totally positive about the way I figured the current through each individual resistor, but anyway...

The total resistance of two resistors in parallel is (R1 * R2)/(R1 + R2), which in this case gives us 12.667. Voltage is common to resistors in parallel, so we can decide that the TOTAL current thru the two parallel resistors is 3/12.667 = 0.237. Current thru any particular resistor is proportional to its share of the load, so R2 would get half the current that R1 gets, so 1/3 * 0.237 = 0.079 (current thru R2), and 2/3 * 0.237 = 0.158 (current thru R1).

If I'm wrong, somebody please correct me.
Click to expand...

Yes this is the correct solution.

Originally posted by: Xylitol
Yea it makes sense now but my brain is dead at almost 3:00 and i cant find voltage...
I just plugin for Ohm's Law right?
Click to expand...

To find the voltage of the battery, V = I*(R1||R2+R3)=0.237*(12.67+10)=5.37
 
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