I found the answer to this problem, but I don\'t understand it. 1. for series in

Question

I found the answer to this problem, but I don't understand it.

1. for series in parallel, 1/Req= 1/R1+1/R2, etc. In step 2 this says 1/Req=1/7.5+1/(6.2+12).

Why is it 6.2+12? Why wouldn't it just be the two that are in parallel - 1/Req=1/7.5+1/12?

Do you do it like 6.2 and 12 are in series so it would be 6.2+12 then they are parallel to 7.5. so is that where you get 1/7.5+1/(6.2+12)?

2. Req= 16.3 and I=V/Req, so I or the total current is 15V/16.3=0.92A

I understand this, but how is this the I for R11? wouldn't the current (I) of resistor 11 be equal to 15V/11 ohms

and the I of resistor 7.5 be equal to 15V/7.5 ohms and the I of resistors 6.2 and 12 equal 15V/(6.2+12 ohms)?

I sort of understand through step 4, but I get lost at step 5. The net current flowing through the circuit is 0.92 A. How is the net current the current that is flowing through resistor 11? Can you explain steps 5 and 6 in detail and answer these questions? Thank you!

Explanation / Answer

1. To find the equivalent resistance, it might help to break it up into multiple steps. The 6.2 resistor and the 12 resistor are in series so R of 2 and 3 = 6.2 + 12 = 18.2. Then you treat those resistors like they are one resistor in parallel with the 7.5 resistor. So, 1/[(1/18.2) + (1/7.5) = 5.3 ohms. Then you can treat the 6.2, 12, and 7.5 resistors as one resistor with a resistance of 5.3 ohms that is in series with the 11 ohm resistor. Then you simply add 5.3 + 11 = 16.3 ohms for the total resistance. 2. Two rules to remember are that 1.) across a resistor in series, the current is the same and the voltage is different across each resistor 2.) across a resistor in parallel, the voltage is the same but the current is different for each resistor. If you apply these rules to the calculations i hope you will be able to understand them better! :)

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