Potential Divider - Online Calculator
A potential divider is the simplest way of producing a source of lower e.m.f. from a source of higher e.m.f.
The output voltage from a potential divider can be calculated as
Uout = Uin R2 / (R1 + R2) (1)
where
Uout = output voltage (V)
R = resistance (Ohms, Ω)
Uin = input voltage (V)
Example - Potential Divider - High Power Consumption
The output voltage from a potential divider with two resistors R1 = 10 ohms and R2 = 20 ohms and input voltage 12 V can be calculated as
Uout = (12 V) (20 Ω) / ((10 Ω) + (20 Ω))
= 8 (V)
The current through the potential divider R1 and R2 (ex. output current) can be calculated by using Ohm's law
I = U / R
= (12 V) / ((10 Ω) + (20 Ω))
= 0.4 A
The power consumption of the divider can be calculated
P = U I
= (12 V) (0.4 A)
= 4.8 W
Example - Potential Divider - Lower Power Consumption
The output voltage from a potential divider with two resistors R1 = 1000 ohms and R2 = 2000 ohms and input voltage 12 V can be calculated as
Uout = (12 V) (2000 Ω) / ((1000 Ω) + (2000 Ω))
= 8 (V)
The current through the potential divider R1 and R2 (ex. output current) can be calculated by using Ohm's law
I = U / R
= (12 V) / ((1000 Ω) + (2000 Ω))
= 0.004 A
The power consumption of the divider can be calculated
P = U I
= (12 V) (0.004 A)
= 0.048 W
The power consumption in a potential divider can be reduced by increased resistance.
Potential Divider - Calculator
Potential Divider Nomogram
The nomogram below can be used to estimate a potential divider.
The default values in the nomogram abocve are for Uin = 12 V, R2 = 47 ohm and Uout = 3.3 V. Since the sum of the resistances (R1 + R2) according the nomogram is approximately 170 ohm - the resistance R1 can be calculated as
R1 ≈ (170 ohm - 47 ohm)
≈ 123 ohm.
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