Question

an electric lamp whose resistance is 20 ohms and the conductor of 4 ohms resistance are connected to a 6 volt battery calculate the total resistance of current a, the current through the current b, the potential difference across the electric lamp and conductor c

Answer 1

In solving this equation let us put some variable :
R is total resistance =
 R1 resistance = 20 ohms
r internal resistance = 4 ohms
 total resistance is given by the formula 

    $\frac{1}{R} = \frac{1}{r} + \frac{1}{R1 \neq }$

therefore the total resistance :
    =[tex] \frac{1}{20} + \frac{1}{4} [/tex]
    = 0.05 +0.25
   = 0.3
To get total Resistance we take the reciprocal

[tex] \frac{1}{R} =0.3 [/tex]
 
 = 3.3 ohms 
I=$\frac{V}{R} = \frac{6}{3.3} =1.81 A$

Using the formula we can calculate the EMF( ε)

ε=V+Ir

= 6+ 1.8*4
=13.2 v