Go Down

Topic: voltage drops... across a resistor. (Read 978 times) previous topic - next topic

Grumpy_Mike

Have a look at this
http://www.thebox.myzen.co.uk/Raspberry/Understanding_Outputs.html
It talks about internal impedance of batteries and any power source in general.

fungus


50 (edit) ma current flowing through the circuit, how's that a 5v drop across the resistor?  


Because of the laws of the universe (and in particular Ohm's law), that's how.
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

cjdelphi



50 (edit) ma current flowing through the circuit, how's that a 5v drop across the resistor?  


Because of the laws of the universe (and in particular Ohm's law), that's how.




Ohms law may not one day may not "apply" to all.

BillHo


Ohms law may not one day may not "apply" to all.

Ohms law was correct all the time but the world was not perfect, voltage source had internal impedance, even the connection wire that you used had resistance.

tack

You have to remember real life isn't the same as the 'perfect' circuit.

As Mike says, a power source may have an internal impedance.

If measuring using an instrument then that will have an impedance too.

Both of these can affect what you may measure in a real-life circuit vs what you calculate.

You have to be aware of these factors to understand why initial calculation and measurements may not agree. Once you understand the extra factors then you can add those into your calculations and find agreement, within certain inherent tolerances.

Go Up