A 4.0-Ω resistor is connected to a 12-Ω resistor and this combination is connected to an ideal dc power supply with voltage V as shown in the figure.If the total current through this circuit is I = 2.0 A,what is the value of voltage V?
A)2.0 V
B)3.0 V
C)6.0 V
D)1.5 V
E)8.0 V

Question

A 4.0-Ω resistor is connected to a 12-Ω resistor and this combination is connected to an ideal dc power supply with voltage V as shown in the figure.If the total current through this circuit is I = 2.0 A,what is the value of voltage V? 
A)2.0 V 
B)3.0 V 
C)6.0 V 
D)1.5 V 
E)8.0 V

Quizplus · Accepted Answer

Using Ohm's law, we can find the voltage drop across each resistor as:
V = IR

For the 4.0-Ω resistor: 
V1 = IR1 = (2.0 A)(4.0 Ω) = 8.0 V

For the combined resistance of the 4.0-Ω and 12-Ω resistors: 
V2 = IR2 = (2.0 A)(4.0 Ω + 12.0 Ω) = 32.0 V

Therefore, the voltage across the power supply must be equal to the sum of the voltage drops across the resistors: 
V = V1 + V2 
V = 8.0 V + 32.0 V = 40.0 V

Therefore, the value of voltage V is 6.0 V (choice C).

A 40-Ω Resistor Is Connected to a 12-Ω Resistor and This