Are you:

a) a comedian,

b) some kind of troll

c) a victim of Asperger's Syndrome

d) other?


A whole paragraph for part-per-billions rounding error? I don't want to start laughing and be mean in case the answer is "c". If it is "c", I am truly interested in how do you make it through a day if this amount of "error" was worth a paragraph?

Do you do things like carefully select items when shopping so the total can be multiplied by the 2.9% state sales tax comes out to a perfect cent with no rounding error? Do you bring your own certified scale to the market when you buy blueberries to make sure you are not getting ripped off? Do you record your odometer and fuel purchases in a little notebook - then calculate and record your mileage to 11 digits of "accuracy"?

You are the one that is trolling. Again. So I'm going to decline your latest attempt to drag me into another of your pointless diatribes.

 

You are the one that is trolling. Again. So I'm going to decline your latest attempt to drag me into another of your pointless diatribes.

So that leaves "c" or "d".

 

So that leaves "c" or "d".

You're wasting your time because I'm not going to play your childish game.

 

You're wasting your time because I'm not going to play your childish game.

Then who's childish game were you playing?

 

OK my last questions

1. Let's say I have 9 volt battery and directly charge a phone without going through any circuit or charger --- would it damaged the phone or no?
If yes can a resistor prevent the damage and provide enough voltage

2. Using 9 volt battery to power up an LED let say LED only require 3 volt to light up...what is the resistor rating to use to prevent the 9 volt to damage the LED

 

Please...back to the topic and try to keep personalities out of it. At least one bystander has complained and I can understand that.

 

OK my last questions
1. Let's say I have 9 volt battery and directly charge a phone without going through any circuit or charger --- would it damaged the phone or no?

There's a chance that it could. The phone expects to see a 5V charge source, not 9V. While I doubt that it truly would do damage, I wouldn't try it with my phone.

If yes can a resistor prevent the damage and provide enough voltage

Not really, no. The phone is not a passive device. It is actively adjusting its charging behavior based on what voltage it sees at the port. So it might start charging if it sees 9V (since no current was flowing initially, the resistor was not dropping voltage, see Ohm's law) but the moment charge current begins to flow, the voltage will drop. I think it would be nearly impossible to get a reliable arrangement. For one thing, a 9V battery may not be able to sustain the charge current demanded by the phone.

2. Using 9 volt battery to power up an LED let say LED only require 3 volt to light up...what is the resistor rating to use to prevent the 9 volt to damage the LED

Ohm's law is your friend. You need the resistor to drop 6V out of the total 9V, with 3V being dropped across the LED. A typical LED will be well lit at 10mA, or 0.01A. Applying ∆V = I•R, you have 6V = 0.01A • RΩ. Rearrange to solve for R. You can then adjust up or down to get to a standard value. So if R works out to 352Ω, you can look at 330, 390 or even 470Ω. Going up is always safe – it will just dim the LED. Don't go down in ohms value without double-checking your calculation. The LED might be destroyed if you go over 20mA.
Note that a 9V battery may not be 9V. Measure it.

 

A whole paragraph for part-per-billions rounding error?

To be fair, read the title of this thread. I don't think the title reflects what the TS was really asking, but the title of the thread did ask what it is, exactly.

 

Thank you all i think i got 90% of the idea of what exactly amp especially credit to wayneh, WBahn, Marley etc who provided quite an insightful input. i appreciate all your effort and time to reply to my questions...the rest of the 10% i will experiment it myself to complete the understanding. gracias muchas a todos...ciao!!

 

To be fair, read the title of this thread. I don't think the title reflects what the TS was really asking, but the title of the thread did ask what it is, exactly.

That's what amused me about the Mod reading only a title and jumping in with answer that is orthogonal to the OP's actual question in post 1.

Taking the time to understand what a rookie OP actually says and what he is trying to learn are the role of an expert. Running with a rookies literal words results in a confusing thread.

 

True dat.

 

That's what amused me about the Mod reading only a title and jumping in with answer that is orthogonal to the OP's actual question in post 1.

Taking the time to understand what a rookie OP actually says and what he is trying to learn are the role of an expert. Running with a rookies literal words results in a confusing thread.

What? We can't walk and chew gum too?

 

What? We can't walk and chew gum too?

Let me clarify,
"Running with a rookie's literal words results in a confusing thread for the rookie who must cull our actual answers from the chaff"