Which device increases voltage by connecting batteries in series?

• A. Potentiometer
• B. Rheostat
• C. Regulator
• D. Toggle switch

Answer: (A)

When you connect multiple voltage sources in series, their voltages add up, giving a higher total voltage across the outer terminals. The items listed here don’t create a higher voltage by wiring sources in series. A potentiometer is a variable resistor used to adjust voltage in a circuit as a divider, not to boost the supply voltage. A rheostat also changes current by varying resistance, not by increasing voltage. A regulator aims to keep output voltage steady, not to raise it. A toggle switch simply opens or closes a circuit with no effect on voltage levels. So the increase in voltage from a series arrangement comes from the sources themselves, not from any of these components.