# Finding the element inside a box

Discussion in 'Homework Help' started by indu407, Aug 10, 2009.

1. ### indu407 Thread Starter New Member

Aug 10, 2009
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0
you have given a box, and it contains one element( resistor/inductor/capacitor) with wires connected to both ends of the elements.
you need to identify whether the given element is resistor/inductor/capacitor. however you can use voltagesource,ammeter and voltmeter.

2. ### StayatHomeElectronics Well-Known Member

Sep 25, 2008
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Consider what happens at the time when you connect the voltage source to the box. What changes as time continues? What happens when you disconnect the source from the box?

For a resistor, when you connect a voltage source the governing equation will be V = i*R. Current, i, flows as long as the source is connected.

From what you know about capacitors and inductors, how does the voltage and current change over these elements when a source is applied?

3. ### mik3 Senior Member

Feb 4, 2008
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Can you use an oscilloscope?

4. ### KL7AJ Senior Member

Nov 4, 2008
2,013
273
If it's anything other than a resistor in the box, you will need an AC voltage source of some sort. They you can figure out the reactance (and impedance) by using the AC impedance formula Z=e/i. It MIGHT be possible to use the RC time constant, if it's a large value of capacitance, or the R/L time constant if ther's a large inductor.

If you apply 120V ac to the terminals and the box explodes, it's probably an electrolytic capacitor inside.

Eric the Practical.

5. ### t06afre AAC Fanatic!

May 11, 2009
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I guess this question is somewhat hypothetical. And the question is more related to StayatHomeElectronics answer. How does how does the voltage and current change over these elements when a source is applied?

6. ### StayatHomeElectronics Well-Known Member

Sep 25, 2008
864
40
It's always a good answer if it make you laugh though. This one did it for me!