Electrical Engineering - Series Circuits - Discussion

Discussion :: Series Circuits - General Questions (Q.No.4)

4. 

A certain series circuit consists of a 1/8 W resistor, a 1/4 W resistor, and a 1/2 W resistor. The total resistance is 1200 . If each resistor is operating in the circuit at its maximum power dissipation, total current flow is

[A]. 27 mA
[B]. 2.7 mA
[C]. 19 mA
[D]. 190 mA

Answer: Option A

Explanation:

Total P = P1 + P2 + P3 = 7/8w.

P = I2R.

I = sqrt (P/R)

Now, P = 7/8w, R = 1200 ohm.

Therefore,

I= sqrt ( (7/8)/1200 ) = 0.0270030862 = 27 mA.


Parashakthi P R said: (Dec 20, 2010)  
P=I2R

Katta said: (Dec 27, 2010)  
Nice explanation.

Sousheelya said: (Jan 4, 2011)  
Appropriate explanation.

Raju said: (Feb 2, 2011)  
Its good.

Raut Mahesh said: (Jun 28, 2011)  
P=P1+P2+P3
P=(1/8)+(1/2)+(1/4)
P=(1+2+4)/8
P=7/8 W
& we have
P=I^2*R

Now P=7/8 w & R is given i.e. R=1200 ohm

Therefore,

I=sqrt(P/R)

I=sqrt((7/8)/1200)

I=27 mA

Sibananda Chakra said: (Jul 6, 2011)  
Thank you nice explanation.

Jay Chhalaliya said: (Sep 21, 2013)  
But in parallel circuit formula of total power.

1/P = 1/P1+1/P2+1/P3.

Dilip said: (Feb 8, 2014)  
p = p1+p2+p3 = (1/8+1/2+1/4) = 7/8.
And, p = i^2*r,
And r = 1200,
i = sqrt(p/r).

Sqrt(7/8)/1200

i = 27mA.

Thanushree said: (Feb 18, 2015)  
I can't understood this problem please explain.

Selvaraj said: (Jul 30, 2015)  
Super and use full explain.

Adil said: (Jul 30, 2015)  
P = P1+P2+P3.

P = (1/8)+(1/2)+(1/4).

P = (1+2+4) /8.

P = 7/8 W.

& we have P = I^2*R.

Now P =7/8 w & are is given i.e. R = 1200 ohm.

Therefore,

I = sqrt (P/R).

I = sqrt ((7/8)/1200).

I = 27 mA.

Prince said: (Aug 24, 2015)  
P = P1+P2+P3= 1/8+1/4+1/2= (1+2+4)/8;

P = 7/8.

We know that P = I^2R ; 7/8 = I^2x 1200;

Then, I = sqrt (7/8)/1200 = 0.027003 A = 27.003m A.

Punith said: (Feb 16, 2016)  
How to calculate sqrt (7/8)/1200 without calculator anybody please?

Veena said: (Feb 28, 2016)  
Nice @Punith asked the good question because in competitive examination calculator is not allowed. So anyone will explain how to calculate square roots without calculator?

Pavan said: (Jun 1, 2016)  
Yes @Punith, same doubt for me.

How to calculate the square root value without a calculator?

Vishal said: (Jul 3, 2016)  
Same doubt for me also, anybody tell me please.

Rishika said: (Sep 23, 2016)  
I don't know how to calculate in calculator can anyone help us who are having trouble about this, please.

Riya said: (Nov 8, 2016)  
@All.

What does sqrt mean?

Ankur said: (Nov 13, 2016)  
@Riya.

sqrt means square root.

Jagan said: (Nov 20, 2016)  
Actually, the parallel circuit formula is 1/p.

Susanta said: (Dec 15, 2016)  
When power are series it calculate as equivalent capacitance.

Megharaj said: (Feb 16, 2017)  
How to calculate sqrt (7/8) /1200 without calculator? Anybody, please tell me.

Chaman Chauhan said: (May 17, 2017)  
How it come sqrt of (7/8)/1200= 0.027003?

Please describe.

Vipin said: (Oct 12, 2018)  
Please explain the last step of this answer.

Subhash said: (Nov 14, 2018)  
How it come √(7/8)/1200= 0.027003?

Please describe.

Yuvaraj said: (Apr 16, 2019)  
The current is same for all the components in a series circuit and here, all three resistors have different power ratings which means only one of the three resistor is operating at its maximum power dissipation and others are consuming less or more amount of power compared their power rating.

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