Battery Voltage as Electromotive Force (EMF)

Steps:

• Voltage on a battery label indicates its electromotive force (EMF), the maximum potential difference it can provide.
• EMF is defined as the electrical energy supplied by the battery per unit charge, in joules per coulomb (V = J/C).
• For a 9V battery, this means 9 joules of energy per coulomb of charge flows through the entire circuit, including internal losses.
• Evaluate options: A matches the full energy supply definition; others misapply to external or loaded conditions.

Why A is correct:

• By definition, EMF ε = W/Q, where W is the total energy supplied by the battery per coulomb Q to the whole circuit.

Why the others are wrong:

• B: Refers only to external circuit energy, excluding internal resistance losses, so it's less than 9J/C under load.
• C: Potential difference across a component depends on circuit resistance and current, not fixed at 9V.
• D: Terminal potential difference drops below 9V due to internal resistance when current flows.

Final answer: A