asic Electrical Engineering A Universal Serial Bus (USB) port is a common feature on both desktop and notebook computers as well as many handheld devices such as MP3 players, digital cameras, and cell phones. The USB 2.0 specification (org(Links to an external site.) (Links to an external site.)) permits data transfer between a computer and a peripheral device at rates up to 480 megabits per second. One important feature of USB is the ability to swap peripherals without having to power down a computer. USB ports are also capable of supplying power to external peripherals. A USB cable is a four-conductor cable with two signal conductors and two conductors for providing power. The amount of current that can be provided over a USB port is defined in the USB specification in terms of unit loads, where one unit load is specified to be 100 mA. All USB ports default to low-power ports at one unit load, but can be changed under soft-ware control to high-power ports capable of supplying up to five unit loads or 500 mA. a. A 680 mAh lithium-ion battery is standard in a Motorola RZZR®. If this battery is completely discharged (i.e., 0 mAh), how long will it take to recharge the battery to its full capacity of 680 mAh from a low-power USB port? How much charge is stored in the battery at the end of the charging process? b. A third-generation iPod® with a 630 mAh lithium-ion battery is to be recharged from a high-power USB port supplying 150 mA of current. At the beginning of the recharge, 7.8 C of charge are stored in the battery. The recharging process halts when the stored charge reaches 35.9 C. How long does it take to recharge the battery?
Basic Electrical Engineering
A Universal Serial Bus (USB) port is a common feature on both desktop and notebook computers as well as many handheld devices such as MP3 players, digital cameras, and cell phones. The USB 2.0 specification (org(Links to an external site.) (Links to an external site.)) permits data transfer between a computer and a peripheral device at rates up to 480 megabits per second. One important feature of USB is the ability to swap peripherals without having to power down a computer. USB ports are also capable of supplying power to external peripherals. A USB cable is a four-conductor cable with two signal conductors and two conductors for providing power. The amount of current that can be provided over a USB port is defined in the USB specification in terms of unit loads, where one unit load is specified to be 100 mA. All USB ports default to low-power ports at one unit load, but can be changed under soft-ware control to high-power ports capable of supplying up to five unit loads or 500 mA.
a. A 680 mAh lithium-ion battery is standard in a Motorola RZZR®. If this battery is completely discharged (i.e., 0 mAh), how long will it take to recharge the battery to its full capacity of 680 mAh from a low-power USB port? How much charge is stored in the battery at the end of the charging process?
b. A third-generation iPod® with a 630 mAh lithium-ion battery is to be recharged from a high-power USB port supplying 150 mA of current. At the beginning of the recharge, 7.8 C of charge are stored in the battery. The recharging process halts when the stored charge reaches 35.9 C. How long does it take to recharge the battery?
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