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Ohms Law

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biferi

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I need to find the type of Resistor I need so I know the Formula is E over I = R but I need some help.

My Current is 20mA and my Voltage is 4000mV and yes I know you first write 20mA as .020 Amp.

Now I know 4000mV is in one Volt.

But would I not write 4000mV as .0004 Volts?

Then do the E over I to get my R in Homs?

You see my Amps are 20mA so I write it as .020 so I thought I would do the same with my 4000mV I would write it as .0004 Volts?
 
You see my Amps are 20mA so I write it as .020 so I thought I would do the same with my 4000mV I would write it as .0004 Volts?
You are not doing the same thing.
If 20mA equals 0.02A, then 4000mV has to equal 4.000V.
 
1mV = 0.001V

4000mV = 4000 x 0.001V = you work it out.

JimB
 
R (ohms) = V (volts)/A (Amps)

R= 4000 mV/20mA ; 4000/20 = 400/2 or 200 ohms.

Since 4000 mV * 1 V/1000 mV and 20 mA * 1 A/ 1000 mA; the 1000's cancel

So, R is also 4 V/0.020 0r 200 Ohms

R is actually a new unit composed of the ratio of V to I.
 
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