Ohm's Law: Increasing resistance reduces circuit current

Steps:

• Increasing the variable resistor's resistance decreases total current in the series path (I = V/R).
• Lamps, in parallel branches, receive less current, reducing their brightness.
• The motor, also current-dependent, receives less current, slowing its rotation.

Why B is correct:

• Ohm's Law dictates that higher resistance lowers current flow, dimming lamps and slowing the motor due to reduced power.

Why the others are wrong:

• A: Motor speeds up incorrectly; less current slows it.
• C: Lamps dim with reduced current, not stay the same.
• D: Lamps dim with reduced current, not stay the same.

Final answer: B