Question

please guys please



Derrive an expression for the equivalent resistance of these resistors R1 ,R2 and R3 connected series.

Answer 1

Total potential difference across a combination of resistors in series is equal to the sum of potential difference across the individual resistors. 

 V = V1 + V2 + V3 

Let I be the current in the circuit. The current through each resistor is also I. It is possible to replace the three resistors joined in series by an equivalent resistor of resistance R. Applying Ohm's law, 

V = IR

 On applying Ohm's law to the three resistors respectively we further have 

V1 = IR1

 V2 = IR2 
V3 = IR3 



But              V = V1+ V2 + V3

                       IR = IR1 + IR2 + IR3

equivalent resistance is ,
Req=R1 +R2+R3

Answer 2

Rs=R1+R2+R3
In series connection the equivalent resistor is the sum of individual resistors.