# Potential Divider - Online Calculator

## Output voltage from a potential divider

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

U_{out}= U_{in }R_{2 }/ (R_{1}+ R_{2}) (1)

where

U_{out}= output voltage (V)

R = resistance (Ohms, Ω)

U_{in}= input voltage (V)

### Example - Potential Divider - High Power Consumption

The output voltage from a potential divider with two resistors *R _{1} = 10 ohms* and

*R*and input voltage

_{2}= 20 ohms*12 V*can be calculated as

* U _{out} = (12 V) (20 Ω) / ((10 Ω) + (20 Ω)) *

* = 8 (V)*

The current through the potential divider *R _{1}* and

*R*(ex. output current) can be calculated by using Ohm's law

_{2}*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 *R _{1} = 1000 ohms* and

*R*and input voltage

_{2}= 2000 ohms*12 V*can be calculated as

* U _{out} = (12 V) (2000 Ω) / ((1000 Ω) + (2000 Ω)) *

* = 8 (V)*

The current through the potential divider *R _{1}* and

*R*(ex. output current) can be calculated by using Ohm's law

_{2}*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

* input voltage (volts)*

* resistor R _{1} (ohm)*

* resistor R _{2} (ohm)*

#### Potential Divider Nomogram

The nomogram below can be used to estimate a potential divider.

The default values in the nomogram abocve are for *U _{in} = 12 V*,

*R*and

_{2}= 47 ohm*U*

_{out}=

*3.3 V*. Since the sum of the resistances

*(R*according the nomogram is approximately

_{1}+ R_{2})*170 ohm*- the resistance

*R*can be calculated as

_{1}*R _{1} ≈ (170 ohm - 47 ohm) *

* ≈ 123 ohm.*