Potential Divider Voltage Formula

Steps:

• Total resistance in series is R1 + R2.
• Current I = battery voltage / (R1 + R2).
• Voltage V1 across R1 is I * R1 = battery voltage * [R1 / (R1 + R2)].
• To increase V1, increase the ratio R1 / (R1 + R2) by raising R1 or lowering R2.

Why B is correct:

• Increasing R1 raises the numerator while decreasing R2 lowers the denominator, directly increasing the ratio per the potential divider formula V1 = V * [R1 / (R1 + R2)].

Why the others are wrong:

• A: Both larger increases total resistance but ratio stays similar or decreases slightly, not guaranteeing V1 increase.
• C: R1 smaller decreases numerator; R2 larger increases denominator, decreasing ratio.
• D: Both smaller decreases ratio toward 0.5 or less, reducing V1 if R1 was dominant.

Final answer: B