# Electronics - Series-Parallel Circuits - Discussion

### Discussion :: Series-Parallel Circuits - General Questions (Q.No.8)

8.

With 21 V applied, if R1 = 5 ohms, R2 = 35 ohms, and R3 = 14 ohms, what is the current of R2 if R1 is series connected with parallel circuit R2 and R3?

 [A]. 200 mA [B]. 800 mA [C]. 600 mA [D]. 400 mA

Explanation:

No answer description available for this question.

 Maddy said: (Apr 18, 2011) May be the answer is 600ohm Plz check someone and explain if answer is 400ohm.

 Swastik said: (Jun 3, 2011) R2 & R3 are in parallel and then in series with R1 Solving, Eq Resistance = 15ohm Then V(given)=21 V So I=V/R=21/15 = 1.4Amp Current across R2(By Current Divider Rule Formula) = 1.4 x 14(R3)/(35+14)= 0.4Amp = 400 mA

 Orange said: (May 23, 2014) By applying mesh analysis at each loop. 40I1-35I2=21---->eqn(1). -35I1+49I2=0----->eqn(2). RESOLVING BOTH WE GET, I1=1.1amp and I2= 1.5amp. current at R2 is I1-I2 =====> 1.5-1.1=0.44amp=400mA.

 James Adams said: (Apr 23, 2015) Where did the 15 ohms come from?

 Jhedd said: (Aug 10, 2015) It is the total resistance.

 Pankaj said: (Aug 12, 2015) 1st calculate the total Resistance. Rt = R1+R2||R3. = 5+(35*14)/35+14 = 15. According to voltage divider: Voltage across R1 is V1 = v*R1/Rt. V1=21*5/15=7. Then voltage across the parallel circuit is 21-7=14; Then current across I2 = 14/R2 = 14/35 = 0.4 A or 400 mA.

 Chinmay said: (Feb 20, 2016) I satisfied with your explanation.

 Deepthi said: (Aug 31, 2016) Thanks @Pankaj.

 Happy said: (Sep 15, 2016) Thanks, @Pankaj. Your explanation is very nice.

 P@\$Hoo said: (Oct 19, 2016) Nice explanation @Pankaj.

 Kamran said: (Oct 27, 2016) Thanks @Pankaj.

 Lester said: (Dec 17, 2016) Not getting, please explain the solution.

 Tayyab Rehaman said: (Mar 25, 2017) Good explanation, Thanks @Pankaj.

 Manish said: (Apr 13, 2017) If a series"parallel circuit has all 30-ohm resistors, what is the total resistance when R1 is in series with a parallel circuit consisting of R2 and R3? * 45 * 50 * 60 * 90 Please give me the answer.

 Damchi said: (May 23, 2017) Loop1: V =i1(R1+R2) - i2R2. => 21=40i1-35i2 ---------1. Loop2: - i1R1+i2(R2+R3) =0. => - 35i1+49i2=0. => i1=(49/35)i2=(7/5)i2-------2. Solving 1 and 2, i2 = 1 A i1 = 1.4 A. Current through R2 = i1-i2 = 0.4 A = 400 mA.

 Vishal said: (Aug 31, 2018) Nice explanation @Pankaj.

 Gurcharn said: (Feb 1, 2019) I think 600 mA.

 Red said: (Mar 17, 2020) In a circuit, R1 and R2 are connected in series having a resistance of 5 ohms and 10 ohms respectively. The voltage across resistor R1 is equal to 4 V. Find the current passing through R2 and the voltage across the same resistor. Please help.

 Red said: (Mar 17, 2020) A parallel circuit has three branches of 6 ohms, 12 ohms, and 20 ohms. If A of current flows through the 12-ohm branch, what is the current flow through the 20-ohm branch?

 Red said: (Mar 17, 2020) A lamp rated at 120 V, 100 W is to be used on a 220 V line. What size of the resistor should be connected in series with the lamp for correct operation?

 Red said: (Mar 17, 2020) A store lightning system consists of 25 lamps of 100 watts each connected in parallel with 120 V sources. What is the total resistance of this system?