A student connects a buzzer to a battery in a simple series circuit. The potential difference across the buzzer is 6 V and a charge of 10 C passes through it in a certain time. Explain what is meant by a potential difference of 6 V across the buzzer, and describe the energy transfer that occurs as the charge flows through it.

A potential difference of 6 V means that 6 joules of electrical energy are transferred for every coulomb of charge that moves between the two terminals of the buzzer. In this circuit the battery supplies 6 V across the buzzer, so each coulomb of charge that passes through the buzzer carries 6 J of energy. When the 10 C of charge flows, 60 J of electrical energy is transferred from the battery to the buzzer. Inside the buzzer this electrical energy is converted into sound energy (and a small amount of heat), so the battery’s electrical energy is ultimately transformed into acoustic (and thermal) energy in the buzzer.