Electronics - Parallel Circuits - Discussion

Discussion Forum : Parallel Circuits - General Questions (Q.No. 25)
25.
Which component is open?

mcq4_1011_1.gif
R1
R2
R3
R4
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
17 comments Page 1 of 2.

Subedar Sk shakya said:   1 decade ago
As we know in parallel circuits current divides& voltage remains same here the first amp meter shows 0.021A is the total current flowing through the R1,R2,R3,R4 and second one shows the current flowing through R3&R4

Now current reading for first one r1*r2/r1+r2=1*2/1+2 =2/3 I=V/R so(12)/(2/3)= 18ma now remains 3ma for second one so it clearly shows again I= V/R =12/4k=3ma So no need of R3.
Here R3 is Open.

Sreeyush Sudhakaran said:   1 decade ago
It=I1=0.021A
I3=0.003A

IR1=12/1K=0.012A
IR2=12/2K=0.006A
IR3=12/3K=0.004A
IR4=12/4K=0.003A

here we can see that IR4=I3 (0.003A) ie no current is flowing through R3

Also It=IR1+R2+IR3+IR4=0.012+0.006+0.004+0.003=0.025 Which is
not correct.

By open circuiting R3 we get It=0.012+0.006+0.003=0.021 which is correct.

So R1 is open in the circuit

Deepti said:   1 decade ago
Total current = 21mA

Current through R1 & R2 = 18mA

So it needs R1 & r2 equivalent = 2/3 which is true.

So R1 R2 not open

Now total voltage acrros last branch = 12v

which is given by R4 ( 4Kohm * 3mA)so there is no need of R3

Hence it is opened.

Mani said:   6 years ago
Here we have a total current of the 21m amp,
Current across R1is.
I1=v/R1=12/1*10^3=12m amp

Current across R2 is;
I2=v/R2=12/2*10^3=6m amp,
Remaining current is 3m amp.

Then current across R4 is,
I3=v/R4=12/2*10^3=3m amp,
Hence resistor R3 is open circuit.

JAGANADHAN.R said:   1 decade ago
Hi,

Total current = 21mA.

Current required by R1 and R2 = 18mA.

So for remaining 3mA(21mA -18mA), R4 = 4K is enough no need for R3.

Thank you.

Kishu said:   1 decade ago
Answer R1 is open because current not flow in R1 because there is short circuit across R1 current always flow in low resistive path.

Priya said:   10 years ago
@Kishu is right. We can't connect volt and ammeters directly because their will be short circuit.

Saurabh said:   1 decade ago
This is not clear how R3 is open connection means only one pole is connected.

Sasi said:   1 decade ago
If R3 get open means R4 also opened.

So, we can get a maximum output.

Hima.V.M said:   8 years ago
It's a clear explanation, Thank you @Deepti.


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