Ohms Law

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?

4000 mV is 4 Volts, so 4/.020 = 200 Ohms.

biferi said:

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?

Click to expand...

You are not doing the same thing.
If 20mA equals 0.02A, then 4000mV has to equal 4.000V.

Beginning to wonder here...

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.