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# 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 VR2 = 47 ohm and Uout3.3 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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### Electromotive Force - e.m.f

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