Question

A cell drives a current of 5A through a 1.6 resistorWhen connected to a 2.8 resistor the current that flows in is 3.2 A.Find the E and r for the cell.

Answer 1

for first I= E/R1+r, 5= E/1.6+r, for second eqn , I'= E/R2+r , 3.2= E/2.8+r,, divide both equation 5/3.2= 2.8+r/1.6+r ,(cross multiple) , 8+5r= 8.96+3.2r , 5r-3r= 8.96-8 , 2r = 0.96 then r = 0.48 ohm , and then putting the value of r in any eqn like 5= E/1.6+0.48 , 5= E/2.08 , E is 2.08×5 , E= 10.4v