Which device is connected directly across the power source due to its high resistance in series with the meter movement?

Which device is connected directly across the power source due to its high resistance in series with the meter movement?

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

Answer: (B)

The key idea is how a voltmeter is built to measure voltage without pulling significant current from the circuit. A voltmeter is designed to have very high input resistance, so it draws only a tiny amount of current. Internally, this high resistance is created by placing a large resistor in series with the meter movement (the galvanometer). When you connect the meter across the power source or across the component you want to measure, this high-impedance path sits in parallel with the circuit, meaning the meter is effectively wired directly across the supply but draws negligible current. That’s why it’s described as being connected directly across the source due to its high resistance in series with the meter movement. Ammeter, by contrast, is placed in series and has very low resistance so it doesn’t drop much voltage. Ohmmeter injects current to measure resistance and is connected across the element to be tested. Wattmeter measures power by combining voltage and current measurements.

The key idea is how a voltmeter is built to measure voltage without pulling significant current from the circuit. A voltmeter is designed to have very high input resistance, so it draws only a tiny amount of current. Internally, this high resistance is created by placing a large resistor in series with the meter movement (the galvanometer). When you connect the meter across the power source or across the component you want to measure, this high-impedance path sits in parallel with the circuit, meaning the meter is effectively wired directly across the supply but draws negligible current. That’s why it’s described as being connected directly across the source due to its high resistance in series with the meter movement.

Ammeter, by contrast, is placed in series and has very low resistance so it doesn’t drop much voltage. Ohmmeter injects current to measure resistance and is connected across the element to be tested. Wattmeter measures power by combining voltage and current measurements.