Electrical Engineering - Series-Parallel Circuits - Discussion

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

8. 

The parallel combination of a 470 resistor and a 1.5 k resistor is in series with the parallel combination of five 1 k resistors. The source voltage is 50 V. The percentage of the load current through any single 1 k resistor is

[A]. 25%
[B]. 20%
[C]. 100%
[D]. 50%

Answer: Option B

Explanation:

No answer description available for this question.

Anand said: (Jul 27, 2011)  
Can anybody explain me about the answer?

Priya said: (Nov 7, 2011)  
470ohm and 1500ohm are in parallel hence effective resitance is=470*1500/1970
=357.87ohm

Parallel combination of 5 1kohm resistors=1000/5=200ohm

Now toatal effective resistance=357.87+200=557.87ohm

Hence current in the circuit=50/557.87=.089amp

Now current throuh 5 1kohm resistors can be divided into two parallelcombination one with resistance 1kohm and other with 1/4kohm...........

Hence by current divider rule current through 1kohm resistor=(.089*1/4)/(1+1/4)=.018amp

Hence % = (.018/.089)*100 = 20%.

Rohit said: (Jan 6, 2012)  
The simplest way is to decide the correct ans. is the total current is passed through five parallel 1k resister equal amount bcoz the same value of resister so 1k current flow=total current (%)/number of resister; 20%.

Snehal said: (Aug 20, 2012)  
Thanks rohit.

Bhasker said: (May 31, 2013)  
@Rohith, Am Not getting your Formula, Could you please expand Once again ?

Jadecliff said: (Jul 28, 2013)  
From Priya calculations, we get:

Current in circuit = .089 A.

Total resistance in parallel combination of 5 1 Kohm resistors = 200 Ohm.

So, voltage in parallel of 5 1kohm resistor = I x R(total res of paralleled 5 resistors).

= .089 x 200.

= 17.8 V.

For parallel combinations, V = V1 = V2 = V3 = V4.

So. V1 = I1 R1.

I1 = V1/R1 = 17.8/(1x10^3) = 0.0178 A.

For percentage, I1/whole circuit current x 100% = 0.0178/.089 x 100.

= 0.2 x 100.

= 20%.

Meena said: (Jan 24, 2014)  
Current I flowing in the circuit will be divided into 5 equal parts (as the 5 equal valued resistors are connected in parallel).

So the current in each branch (of resistor) is I/5.

So the percentage is : (I/5) /I*100 = 20%.

S.C.Mathur said: (Mar 10, 2014)  
I am 100% agree with the solution given by Meena, it is the simplest & quick way of calculation. The total current flowing out from the first parallel combination will flow in the second combination but will get divided in to five equal parts so each part of current will be i/5th of the combination(2nd) total input current which will be 1/5th i.e..2 or.2*100 = 20%.

Anil said: (Jul 22, 2014)  
What about if the resistors connected in parallel are not of same value?

Aayan said: (Sep 19, 2014)  
Then you need to do as explained by @Priya.

Siva said: (Oct 31, 2014)  
@Meena.

You are wrong in parallel current through all branches is not same :).

You are getting the right answer because all resistors are same value so the currents drawn by them is also same :).

Deepu said: (Apr 23, 2015)  
@Meena.

Exactly your right for same set of resistors. And even we can calculate the same in for different resistors values.

Parneet Kaur said: (Jul 9, 2015)  
Of course @Meena you are right.

But this simple and quick method is only applied when all the resistors are of same value. Otherwise you can't applied when resistors are of different values are given.

What is the simple method when resistors are of different values are given?

Shashank said: (Apr 19, 2016)  
Actually, they ask for a percentage. So, for 51K ohms resistor 50V/200ohm = 0.25A.
Again 50/1 Kohm = 0.05A, therefore 0.05/0.25*100 = 20%.

Satish Reddy N said: (Oct 18, 2016)  
@Priya,

Where does that 1/4 comes from I am not getting that?

Puja said: (Jan 11, 2017)  
You are right @Shashank.

But can you tell me what is the formula if there is not same resistance in parallel?

Megha said: (Feb 13, 2017)  
Thank you for the explanation.

Don said: (Feb 22, 2017)  
Thanks for the explanation of the answer.

Vandana said: (May 15, 2017)  
Thank you @Meenakshi.

Richa said: (Sep 2, 2017)  
Please somebody give me current divider formula with explanation.

Samba said: (Jul 9, 2019)  
Thanks @Rohit.

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