electrical equations

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P = E^2 / R

Voltage Divider

Voltage Divider No Load

The voltages are proportional to the resistances.

Vout = Vin * (R2 / (R1 + R2))
Vin = Vout * ((R1+R2)/R2)
     Vout+ O   Vout- O
           |         |
           |         |
      R1   |    R2   |
 +--/\/\/--+--/\/\/--+
 |                   |
 |                   |
Vin+                Vin-

Voltage Divider Under Load

R2 || Rload  =  (R2 * Rload) / (R2 + Rload)

Vout = V1 * ( R2 ||Rload) / (R1 + R2 || Rload)
              Rload
           +--/\/\/--+
           |         |
           |         |
     Vout+ O   Vout- O
           |         |
           |         |
      R1   |    R2   |
 +--/\/\/--+--/\/\/--+
 |                   |
 |                   |
Vin+                Vin-

Vout = Vin (

Picking a value for R1 and R2

Assume you have a restive sensor to test. Out of circuit you would test the sensor to determine its minimum resistance and maximum resistance. Then pick

R2 = sqrt (Rmin * Rmax)