If R2 is changed to 15Ω, what happens to total resistance?

If R2 is changed to 15Ω, what happens to total resistance?

• A. Resistance would decrease.
• B. Resistance would stay the same.
• C. Current would rise.
• D. Resistance would increase.

Answer: (D)

In a series circuit, the total resistance is the sum of all individual resistances. When one resistor is increased, the total also increases. Setting R2 to 15Ω raises the overall resistance, so the total resistance goes up. As a quick note, with a fixed voltage, a higher total resistance would cause the current to fall (I = V / Rtotal). The other options don’t fit because decreasing total resistance or leaving it unchanged would require different changes to the resistors, and a rise in current would occur only if the total resistance dropped.

In a series circuit, the total resistance is the sum of all individual resistances. When one resistor is increased, the total also increases. Setting R2 to 15Ω raises the overall resistance, so the total resistance goes up.

As a quick note, with a fixed voltage, a higher total resistance would cause the current to fall (I = V / Rtotal). The other options don’t fit because decreasing total resistance or leaving it unchanged would require different changes to the resistors, and a rise in current would occur only if the total resistance dropped.