Which statement describes how you measure the potential difference of a cell or battery?

Which statement describes how you measure the potential difference of a cell or battery?

• A. Connect voltmeter in series with the cell
• B. Connect leads to the two terminals of the cell
• C. Connect voltmeter across the entire circuit
• D. Connect voltmeter to measure current

Answer: (B)

Measuring voltage is done by placing the voltmeter across the component you want to know the voltage of. For a cell, that means connecting the voltmeter’s two leads to the cell’s two terminals so it is in parallel with the cell. The meter has high internal resistance, so it draws almost no current and you read the true potential difference without changing the circuit. If the voltmeter were placed in series, it would alter the current and you wouldn’t be measuring the cell’s voltage anymore. Measuring across the entire circuit could include drops from other components, not isolating the cell’s voltage. And a voltmeter measures voltage, not current—that’s what an ammeter is for.

Measuring voltage is done by placing the voltmeter across the component you want to know the voltage of. For a cell, that means connecting the voltmeter’s two leads to the cell’s two terminals so it is in parallel with the cell. The meter has high internal resistance, so it draws almost no current and you read the true potential difference without changing the circuit. If the voltmeter were placed in series, it would alter the current and you wouldn’t be measuring the cell’s voltage anymore. Measuring across the entire circuit could include drops from other components, not isolating the cell’s voltage. And a voltmeter measures voltage, not current—that’s what an ammeter is for.