The shape of the lesson
By the end of the lesson, learners can
- What is USB?: Each word in the name matters.
- Plugging in: This is the sequence the examiners want when they ask how USB is used to transmit data.
- Benefits and drawbacks: Learn a few of each.
- How: serial, one bit at a time.
- On connection: detected automatically, correct driver loaded.
- Benefits: industry standard, auto-detection, supplies power, fits one way, backward compatible.
- Drawbacks: limited cable length, older versions slower, limited power.
One picture every idea returns to
USB (universal serial bus) is an industry standard interface for connecting devices to a computer. It uses serial transmission: data is sent one bit at a time. When a device is plugged in, the computer automatically detects it and loads the correct driver. The cable can also supply power to the device. The main drawbacks are a limited cable length and slower speeds on older USB versions.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, One plug for everything.. Keyboards, mice, printers, flash drives and phones all connect to a computer through the same kind of port. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: What is USB? | Each word in the name matters. Project tab 2 of the lab (Serial transmission and USB) and let a student drive it while the class predicts. | Whole class, then pairs |
| 13 to 21 min | Teach and check: Plugging in | This is the sequence the examiners want when they ask how USB is used to transmit data. Model the worked example A new mouse on the board, one line at a time. | Pairs |
| 21 to 30 min | Teach and check: Benefits and drawbacks | Learn a few of each. Your turn: Give one reason a USB printer cable is unsuitable for connecting a printer 30 metres away. | Frayer Model |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 13 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Benefits and drawbacks, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Frayer Model
Pairs fill a four-box grid for the key term: definition, characteristics, examples and non-examples. The non-examples box is where the misconceptions surface, so give it the most time.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| USB is serial, not parallel. | If a question asks how USB transmits data, "one bit at a time" is the key phrase. |
| "It is fast" is too vague to earn a benefit mark. | Give a specific benefit such as automatic detection, power supply or being an industry standard. |
The universal serial bus (USB): worksheet
6 questions, 13 marks. Written in the style of the papers; no past paper question is reproduced.
State what the letters USB stand for.
Describe how a USB connection is used to transmit data from a flash drive to a computer.
Give three benefits of the USB interface.
Give two drawbacks of the USB interface.
A shop wants to connect a barcode scanner to a till 2 metres away. Explain why USB is suitable.
USB uses serial transmission. Explain why serial transmission is a good choice for a cable that may be up to a few metres long.
Answer key and marking notes
Universal serial bus.
- The computer automatically detects the flash drive when it is plugged in.
- The correct driver is loaded.
- Data is transmitted serially, one bit at a time.
- It is an industry standard, so it works with most devices / computers.
- Devices are automatically detected and drivers loaded.
- It can supply power to the device / connectors can only fit one way / backward compatible (any one).
- The maximum cable length is limited (a few metres).
- Older USB versions have slower transmission speeds / limited power for larger devices.
- 2 m is within the maximum USB cable length.
- The scanner is detected automatically and can be powered by the USB cable, so no extra power supply is needed.
- Bits are sent one at a time, so they arrive in order.
- There is no skew, so the data is less likely to be corrupted than with parallel; fewer wires also make the cable cheaper.
6 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
How is data transmitted along a USB cable?
- ASerially, one bit at a time
- BIn parallel, one byte at a time
- CSerially, one byte at a time
- DIn parallel, one bit per wire
What happens when a new device is first plugged into a USB port?
- AThe computer detects it automatically and loads the correct driver
- BThe user must restart the computer before the device can be used
- CThe device sends its data in parallel until a driver is installed
- DThe computer gives the device a new packet number to identify it
A student charges a mobile phone from a laptop using a USB cable, while also copying photos from the phone. Which feature of USB does this show?
- AThe cable can carry power as well as data
- BData is sent using parallel transmission
- CThe cable can be any length without errors
- DData can only travel in one direction
Which of these is a drawback of USB?
- AThe maximum cable length is limited
- BIt is an industry standard used by many devices
- CDevices are detected automatically
- DThe cable can supply power to devices
A shop wants to connect a barcode scanner, a receipt printer and a card reader to one till computer. Why is USB a good choice?
- AOne standard connection works for all three devices from different makers
- BUSB uses parallel transmission, so it is faster than any other method
- CUSB devices never need a driver to work with the computer
- DUSB cables can link tills in shops in different towns
A newer USB 3 external drive is plugged into an older USB 2 port. Which outcome is most likely?
- AThe drive works, but only at the slower USB 2 speed
- BThe drive does not work until the port is upgraded
- CThe drive works at the full USB 3 speed
- DThe drive switches to parallel transmission to keep its speed
Quiz key
USB stands for universal serial bus and sends data one bit at a time. It is not parallel, so it does not send a whole byte on several wires at once. 'Serially, one byte at a time' mixes the terms up: serial means the bits of each byte follow one another, not that a whole byte moves at once.
USB devices are automatically detected and the right driver is loaded (or the user is prompted to install one). No restart is needed. USB never switches to parallel transmission. Packet numbers belong to network packets, not to identifying USB devices.
USB can supply power down the same cable that carries data, so the phone charges while the photos copy. USB is serial, not parallel. USB cables have a limited maximum length, so 'any length' is false. Photos travelling from the phone while the laptop sends requests to it shows data is not limited to one direction.
USB cables only work reliably over a few metres, so long connections need another method. Being an industry standard, automatic detection and supplying power down the cable are all benefits of USB.
USB is an industry standard, so devices from many manufacturers plug into the same ports and are detected automatically. USB is serial, not parallel. USB devices do need drivers; the advantage is that they are loaded automatically. USB cables are limited to a few metres, so linking shops in different towns would need a network.
USB is backward compatible, so the drive still works, but the transfer speed is limited by the older port. It does not refuse to work, and it cannot reach USB 3 speed through a USB 2 port. USB is always serial; it never switches to parallel.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.