Experiment

116

00:55:49

Can you please tell me what is the power dissipated by each resistor? Thanks :)

published 10 years ago

Sine_eyed

10 years ago

Well, P = V x I. We can plainly see what the current is (I) on each resistor, so determine (V) then just plug it in to the equation and BANG!- there you have (P)..

giomix

10 years ago

2,5 volt * 0,1 ampere = 0,25 watt

giomix

10 years ago

And 1 volt * 0,1 amp ,= 0,1 watt for the blu led

giomix

10 years ago

But resistor are 2 for each line of led, so you have to divide by 2 the powers I indicated before

Sine_eyed

10 years ago

Are you sure about that last part @giomix? If you're just giving away answers, they should be the right ones..

Sine_eyed

10 years ago

@Seductive- knowing the power dissipation of the resistors is only part of the story. "What is P?" is just the first in a series of questions that need to be answered beforehand. Ask yourself, why do I see equal current through each resistor, when they are of different resistances themselves? And why are there different voltages between the resistors and the LEDs? Here's a hint: work your way backwards through the circuit, and apply Ohm's Law at each step along the way..

hurz

10 years ago

P=UxI and U=RxI put this second formula into the first (substitute U) and you get P=RxI x I or P=RxI² the rest is easy. E.g. 0.1A²*10Ohm=0.1W so you are safe if you use 1/2W Metall resistors.

giomix

10 years ago

@sine_eyed, instead write as "a professor during a lesson", please indicate your calc to answer the question.

giomix

10 years ago

Obviously, i was wrong about "divide by 2" only because due a mistake in reading 100ma in main branch instead through each resistor

Seductive

10 years ago

Thank you all guys, I was confused with the voltage, I tought it was 4.5V but actually it's 1V & 2.5V respectively... Thank you for your time and help, really appreciate that. :)

giomix

10 years ago

@seductive: resistor power is given by formula p=r*i*i or the same p=v*i where v is the voltage measured between the two terminals of the resistor. You may add in your circuit a voltmeter connected in parallel to resistor and you may read voltage.

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