Appsloveworld free online voltage drops calculator so that you can calculate voltage drop across resistor,when connected in is a example of voltage divider calculator with 3 can also find voltage divider rule formula.
please enter Input voltage Vresistance  R1,resistance R2,resistance R3 and click on calculate button for obtaining voltage drop
Input total voltage: VT = Volts [V]
Input resistance of first load: R1 = Ohms [Ω]
Input resistance of second load: R2 = Ohms [Ω]
Input resistance of third load: R3 = Ohms [Ω]
Voltage drop (R1): V1 = Volts [V]
Voltage drop (R2): V2 = Volts [V]
Voltage drop (R3): V3 = Volts [V]

How Voltage divider rule works for DC circuit

Lest we have a DC circuit and a constant voltage source VT and all resistors  connected in
series the you can find voltage drop Vi using below formula


Vj- voltage drop in resistor Rj in volts [V].

VT – the equivalent voltage source or voltage drop in volts [V].

Rj – resistance of resistor Rj in ohms [Ω].

R1 – resistance of resistor R1 in ohms [Ω].

R2 – resistance of resistor R2 in ohms [Ω].

R3 – resistance of resistor R3 in ohms [Ω].

R4 – resistance of resistor R4 in ohms [Ω].

Lest take one Example
We have a Voltage source of VT=50V is connected to All resistors in series, R1=20Ω, R2=20Ω,R2=10Ω
So we have to Find the voltage drop on resistor R3.
V2 = VT × R3 / (R1+R2+R2) = 50V × 10Ω / (20Ω+20Ω+10Ω) = 10V

How Voltage divider work for AC circuit
The voltage drop Vi in load Zi is given by the formula:
Lest we have a AC circuit and a constant voltage source VT and  loads are  connected in
series the you can find the voltage drop Vi in load Zi using below formula


Vj- voltage drop in load Zj in volts [V].

VT – the equivalent voltage source or voltage drop in volts [V].

Zi – impedance of load Zi in ohms [Ω].

Z1 – impedance of load Z1 in ohms [Ω].

Z2 – impedance of load Z2 in ohms [Ω].

Z3 – impedance of load Z3 in ohms [Ω].

At any time current flows across a parallel path it gets divided because of presence of electron in  various path.
If The flow path having low resistances will supply less resistance to current flow and more current will move across that path.
In simple word you can say that if current path having high opposition then current flow will
less across this path.
Lets take one more example we have a circuit which having voltage source of 20 volt, and three resistors 5 ohm,10phm and 15 ohm connected in  series and with load of 2 ohms.

using volatge divider formula
V1(in R1) = V(voltage source)*(R1/Requation), Requation= R1+R2+R3+Rload= 5+10+15+2= 32ohms.

V1(in R1) = 20*5/32= 3.125 volt.

V2(in R2)= 20*R2/41= 20*10/32=6.25volt.

V3(in R3) = 20*R3/41=20*15/32= 9.375 volt.

V4(in R4) = 20*R4/41= 20*2/32= 1.25volt.
V= V1+V2+V3+V4= 20 volt

Tats voltage division rule..
In simple words you can explain Voltage divider as “Voltage divider are circuits which can be used to  decrease the voltage in the circuit”

There are numerous biasing method like collector feedback,fixed bias, emitter feedback,voltage divider bias etc.But from all above list voltage divider bias is found to be the most acceptable.
and voltage divider bias the most used biasing method .

Benefit of voltage divider
If we want to reduce the voltage we can use voltage divider.
Let’s take one example example:
20V has to reduced 2V, then we use 1:10 ratio voltage divider. But higher side 20V to 200V you can not do.

  • Voltage dividers are handy for mainrtaing the output voltage of linear regulators.
  • Voltage dividers are also handy for dividing down a high voltage to the input range of an A/D inside a micro-controller.

How to calculate voltage divider


Vout = Vin * R2/R1+R2
Vout/Vin = R2/R1+R2
Vin/Vout = R1+R2/R2
Vin/Vout = R2/R1+R2
Vin/Vout = R1/R2+R2/R2
Vin/Vout = R1/R2+1
Vin/Vout-1 = R1/R2
R2 = R1/(Vin/Vout-1)
R2 = 1000/(12/9-1)
R2 = 3000=3k

Vout = Vin*R2/R1+R2
1    =   6*5/5+R1
1/6  = 5/5+R1
5R1 =  30
R1  =  25k

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