Answers to Problems - The Potential Divider

  1. The diagram below shows a circuit divider consisting of two resistors in series with a supply voltage. Statements (a) through (e) give values for each element of the circuit except one. For each statement, calculate the missing value.


    a) VIN = 60 V,     R1 = 6 Ω,     R2 = 4 Ω

    b) VIN = 20 V,     R1 = 5 Ω,     R2 = 5 Ω

    c) R1 = 10 Ω,     R2 = 5 Ω,     VOUT = 10 V

    d) VIN = 50 V,     R1 = 10 Ω,     VOUT = 10 V

    e) VIN = 20 V,     R2 = 4 Ω,     VOUT = 5 V

    A potential divider consisting of two resistors in series with a supply voltage

    A potential divider consisting of two resistors in series with a supply voltage


a) Find VOUT:

VOUT  =  VIN  ×  R2  =  60  ×  4  =  24 V
R2  +  R14  +  6


b) Find VOUT:

VOUT  =  VIN  ×  R2  =  20  ×  5  =  10 V
R2  +  R15  +  5


c) Find VIN:

VIN  =  VOUT  ×  R2  +  R1  =  10  ×  5  +  10  =  30 V
R25


d) Find R2:

R2  =  VOUT
R2  +  R1VIN

R2  ×  VIN  =  (R2  +  R1)  ×  VOUT


R2  ×  50  =  R2  ×  10  +  100


R2  ×  40  =  100


R2  =  100  ÷  40  =  2.5 Ω




e) Find R1:

R2  =  VOUT
R2  +  R1VIN

R2  ×  VIN  =  (R2  +  R1)  ×  VOUT


80  =  20  +  R1  ×  5


R1  ×  5  =  60


R1  =  60  ÷  5  =  12 Ω