A ____ can be connected directly across the power source because it has a very high resistance connected in series with the meter movement.

A ____ can be connected directly across the power source because it has a very high resistance connected in series with the meter movement.

• A. Ammeter
• B. Voltmeter
• C. Ohmmeter
• D. Wattmeter

Answer: (B)

Voltmeter is designed to draw as little current as possible from the circuit. It uses a very high input resistance (a large series resistance with the meter’s movement) so that when it’s connected directly across a power source, it hardly loads the circuit. Because only a tiny current flows through the meter, the voltage across the source is measured with little disturbance to the circuit’s operation. This is why a voltmeter is connected in parallel across the element whose voltage you want to know. In contrast, an ammeter has very low resistance and is placed in series to measure current, an ohmmeter injects current to measure resistance, and a wattmeter combines both voltage and current measurements to determine power.

Voltmeter is designed to draw as little current as possible from the circuit. It uses a very high input resistance (a large series resistance with the meter’s movement) so that when it’s connected directly across a power source, it hardly loads the circuit. Because only a tiny current flows through the meter, the voltage across the source is measured with little disturbance to the circuit’s operation. This is why a voltmeter is connected in parallel across the element whose voltage you want to know.

In contrast, an ammeter has very low resistance and is placed in series to measure current, an ohmmeter injects current to measure resistance, and a wattmeter combines both voltage and current measurements to determine power.