03-04-85 wrote:
thank you that made lot of sense to me.
in routine office work where is thunderbolt useful..
is the receiving system should be thunderbolt compatible?
Thunderbolt itself would be useful
- If you were using a very-high-resolution display that required Thunderbolt input, like the 27" Apple 5K Studio Display.
- To attach a Thunderbolt dock or hub.
- To drive two displays (with resolutions of up to 4K @ 60 Hz) from a single Mac host port. Macs only support this when the device immediately connected to the port is a Thunderbolt one (like a Thunderbolt dock). The displays hanging off the Thunderbolt dock would not, themselves, need to be Thunderbolt ones.
- To attach extremely-high-speed external SSDs. For office work, external USB SSDs (e.g., USB 3.0 / SATA or USB 3.1 Gen 2 / NVMe) would be fast enough, and much cheaper. Even an external USB hard drive, with its spinning disks, might be fast enough for many office uses.
Is cable used between two devices is different?
To some extent. USB-C cables run the full range from "charging only" cables that don't carry data at all, to ones that carry data at USB 2.0 speeds, to ones capable of carrying DisplayPort video to a 4K monitor, to those which can reliably carry data at Thunderbolt speeds. Ones that support Power Delivery have a separate rating for that.
There are lots of inexpensive third-party cables that can handle USB at up to 10 Gb/s (USB 3.1 Gen 2 speed) and that can support DisplayPort output to a monitor with a resolution of up to 4K @ 60 Hz.
Once you start transmitting data at Thunderbolt or USB4 40 Gbps speeds, you need a high-quality cable like the Apple Thunderbolt 4 (USB‑C) Pro Cable (1.8 m) . That one costs perhaps 8x to 10x as much as an everyday USB cable or display cable. So even though it would work well for lesser applications, you might want to wait to buy it until you are connecting some Thunderbolt or USB4 40 Gbps device that actually needs it.
can either of this ports can be used to charge keyboard, mouse or mobile?
USB 3.0 specifications call for a host to provide up to 4.5W of 5V power (900mA @ 5V). That is enough to charge a mouse or a keyboard; to run a USB flash drive; or to run a typical bus-powered portable hard drive or SSD.
I do not know if the iMac is willing to offer any Power Delivery power – and if so, how much. PD allows negotiation for much larger amounts of power delivery – up to 240W (5A @ 48V). A mobile phone might use PD to draw, say, 20W or so from a USB-C power source; charging at a lower rate if it saw that PD was unavailable. I believe that it is likely that even if the iMac did not offer large amounts of power, a mobile phone would still charge.
NOTE: If you get a dock or hub, get one that has its own power supply. With an unpowered hub, you may run into the issue that the hub, and devices attached to it, try to draw more combined power than a computer has to offer.
