Answer:
Step-by-step explanation:
o calculate the current I, we can use Ohm's Law which states that I = V/R, where V is the total voltage across the resistor and R is the resistance of the resistor.
a) The total voltage across the resistor can be found by adding the voltage of the two batteries in series, which gives a total voltage of 8V + 4V = 12V.
So, I = V/R = 12V/4Ω = 3A.
b) The potential difference Uba is simply the voltage difference between the two batteries in the series combination, which is 8V - 4V = 4V.
c) When switch S is open, the circuit is broken and the potential difference Uba' becomes equal to the voltage of the 8V battery. So, Uba' = 8V.