In which type of circuit is the voltage always the same across all components?

In a parallel circuit, all components are connected across the exact same two electrical points or nodes. Because voltage is defined as the difference in electrical potential between two specific points, sharing these identical connection points means every component must experience the exact same voltage. If you connect three resistors in parallel to a 12-volt battery, each resistor is directly connected to the positive and negative terminals of that battery. Therefore, a voltmeter will read 12 volts across any of those individual resistors. This is the opposite of a series circuit, where the total voltage drops incrementally across each component depending on its resistance. In a series circuit, it is the current that remains the same, not the voltage.