Can usb-c be used to charge older iphones - can usb-c and usb-a be used interchangeably?
can I use usb-a for iphone 11 that was supplied to me with usb-c?
iPhone 11
Yes. Apple encourages you to use the older power adapters and cables. See the following from Buy iPhone 11 - Apple
As part of our efforts to reach our environmental goals, iPhone 11 does not include a power adapter or EarPods. Included in the box is a USB‑C to Lightning cable that supports fast charging and is compatible with USB‑C power adapters and computer ports.
We encourage you to re‑use your current USB‑A to Lightning cables, power adapters, and headphones which are compatible with this iPhone. But if you need any new Apple power adapters or headphones, they are available for purchase.