Electronics - Inductors - Discussion

2. 

In the given circuit, what will the voltage be across R3 25 mu.gifs after the switch is moved to position 2?

[A]. 2.88 V
[B]. 5.9 V
[C]. 8.34 V
[D]. 14 V

Answer: Option B

Explanation:

No answer description available for this question.

Nishant said: (Jan 14, 2011)  
Solution??

Anvm said: (May 4, 2011)  
Please tell me the solution?

Naseem Ul Aziz said: (May 8, 2011)  
Apply voltage divider that is
when switch will be at position 2
v3=((r3)/(r3+r2))*vt=5.6 volt

Ravi said: (Sep 15, 2011)  
Naseem is right.

Isuru_R said: (Jan 3, 2012)  
When the switch is at "1" position
I = 14/(120 + 820)
I = 0.01489
Then we can find the current 25us after the switch is moved to position "2" using the equation I2 = I * e^(-tR/L)
Then... from(R3* I2 ) we get the voltage across the resistor "R3".
Substitute I = 0.01489 A ; t = 25x10^(-6) s ; R = (820 + 560) ;
and L = 0.1 H
Then you will get (I2*R3) = 5.9 V , which gaves us the required solution....!

Sambhaji Gawande said: (Jan 30, 2012)  
Correct solution by Isuru_R.

Latha said: (Mar 18, 2012)  
Naseem then how will you consider the given time?

Preetha said: (Aug 24, 2012)  
@Isuru is correct.

Clint said: (Aug 13, 2013)  
@Isuru, @Sambhaji, @Preetha, could you please solve I2 ? I didn't get the correct answer.

Arun said: (Oct 25, 2013)  
@ clint
Use the formula I2= I * (1- e^-t(R/L))

Mayank said: (Oct 28, 2016)  
Did we ignore inductance when the switch is at position one due to its very less magnitude?

Syed Shams Ul Arifeen Shah said: (Dec 13, 2016)  
@Mayank,

Yes we ignore the inductance because in DC source, frequency is zero so that inductor behave like short wire (XL = 2 * pi * F * L) here F = 0, XL = 0.

Chandhu said: (Jan 2, 2017)  
Open switch are there r1 then why voltage flow r3?

Chandhu said: (Jan 2, 2017)  
Open switch are there r1 then why voltage flow r3?

Ashfaque said: (Apr 21, 2018)  
@All.

An Inductor is a short circuit to dc. Then why we would be bothered about 25 microseconds. I think you are correct @Naseem.

Priyanka said: (Jul 1, 2019)  
@Clint.

I2 = I*(e^(t(R/L)).
Then I2 = 10.54*10^-3.
Therefore voltage across R3 = I2*R3 =5.905 v.

Oliver said: (Dec 23, 2019)  
Yes, but to be clear, inductors are shorted (VL = 0) at DC only when STEADY STATE is reached (around 5 time constants). Though the question did not mention it, it was assumed to be that way which is why its more confusing.

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