Answer:
In this example, if the emf of the 4 V battery is increased to 15 V and the rest of the circuit remains the same, what is the potential difference Vab?
The image of the circuit has been attached
At 12 emf Vab = 9.5 V
At 15 emf Vab = 12.94 V
Explanation:
Kirchhoff loop rule states that the sum of the currents coming into a junction equals the sum of the currents going out of a junction. That is to say that the sum is equal to zero.
Calculations
The voltage in a circuit can be calculated using the expression;
V= IR .............1
since the Applying Kirchhoff rule to the circuit we have;
Calculating Vab (the voltage across ab) when the emf is 12 v
let us obtain the value of the current flowing across the circuit using equation 1 and Kirchhoff loop rule
+12 - (I x 2) -(I x 3)-(I x 4)-(4)-(I x 7) = 0
I = 8/16 = 0.5 A
calculating the voltage across Vab we have;
Vab = 4V + (I x 7) + (I x 4)
Vab = 4V + (0.5 x 7) + (0.5 x 4)
Vab = 4 +3.5+2
Vab = 9.5 V
at 12v emf Vab is 9.5V
calculating Vab at 15 emf value using equation and also Kirchhoff's loop rule we have;
+15 - (I x 4) -(I x 3)-(I x 2)-(12)-(I x 7) = 0
I = 3/16
I =0.1875 A
Vab = 15 V -(I x 7) - (I x 4)
Vab = 15 - ( 0.1875 x 4)-(0.1875 x 7)
Vab = 15 - 0.75-1.3125
Vab = 12.94 V
