A battery supplies a constant voltage, which makes the circuit it drives:

1. The source waveform decides which kind of circuit it is. 2. Most examples using batteries have constant voltage sources. 3. Direct current is the flow of electric charge in only one direction. 4. A periodically varying source would give an alternating current circuit. 5. So a constant-voltage battery drives a direct current circuit. _Source: OpenStax College Physics for AP Courses 2e (CC BY 4.0), Ch 20 'Electric Current, Resistance, and Ohm's Law', sections 20.1-20.7_