What component is essential for the physical connection of expansion cards in a computer?

The motherboard is crucial for establishing the physical connection of expansion cards in a computer. It serves as the primary circuit board that houses the CPU, RAM, and other essential components, as well as providing the slots into which expansion cards can be inserted. These slots—commonly PCI, PCIe, or AGP—allow various components like graphics cards, sound cards, and network cards to interface with the rest of the computer system.

The arrangement and architecture of the motherboard facilitate communication between the CPU and expansion cards, ensuring that data can flow to and from these devices effectively. While the CPU, power supply, and RAM are important for the overall function of a computer, they do not directly provide the necessary physical interface for expansion cards.