The black box puzzle

[lordsathish]

while surfing i found such a question...
i couldn find the answer...
could you help me...
You go to the lab, and connect a battery across the terminals of a black box. Then, using the instruments on the bench, you measure the following:
Voltage across the terminals: 1 V.
Current entering the box: 2 A.
Power dissipation of the box (measured by a watt meter): 0 W.
What is in the box?



Thank you...

 

[Asif2008]

Re: question

nothing in this box

 

[TwinT]

Re: question

if you're in AC, could be an ideal inductor or capacitor, or a combination of both, but without resistors, since P = 0W

Best Regards

 

[barry14]

Re: question

The box could contain a 1 volt battery in series with a 0.5 ohm resistor. If you measure the voltage with a high impedance voltmeter, no current will flow and you will measure the battery voltage of 1 volt. If you measure the current with a zero resistance ammeter, then the current will follow Ohm's law (1 volt/0.5 ohm) and will be 2 amperes. If you measure the power dissipation of the box, it will be zero since no current wil flow if no load is connected to the box's terminals; 0 watts are dissipated.

 

[kiprono]

Re: question

Can you tell us the power source AC or DC? If AC then the box simply has a purely inductive load. If DC then what kind of watt-meter are you using?