Practical tips
When building circuits they can end up looking a bit like a plate of spaghetti. Un-insulated connections may cause short circuits which at best prevent the circuit from working and at worst may damage the components or the micro:bit.
Purchase insulated crocodile clips. From my experience, children are not sufficiently careful when using crocodile clips to prevent them touching each other.
To save money I recommend buying cheap, generic components from suppliers like Maplins, Radio Spares and Farnell.
Connecting an LED:
An LED has to be connected the right way round in a circuit or it will not light. To help with this the lengths of the two 'legs' of the LED are unequal. The longer leg is the positive side of the LED.
The wires you use to connect components do not need to be soldered onto the component. Soldering is not safe for young children to carry out, without very close supervision, so I recommend twisting the wires together. The pictures below show how wires can be attached to an LED.
Note the inclusion of a resistor on the long leg of the LED to limit the current. This is to prevent the resister from being overloaded and damaged.
The insulating tape is to prevent the two legs of the LED from touching and causing a short circuit
Conventionally, red wire is used for the positive side of the circuit and black for negative.
The supplier of your components can advise on the correct rating for the resistor. Follow the link below to learn more about picking resistors for LEDs.
http://www.evilmadscientist.com/2012/resistors-for-leds/
Connections can be made with 4 mm 'banana' plugs, 4 mm spring connectors or crocodile clips. The picture below shows and LED connected to pin 2 with the positive side being connected to the pin and the negative side to GND.
Watch the video on using pins to add electronic devices (buzzer and LED).
There are a number of different ways that components can be connected to the micro:bit. Some are more successful than others. It certainly helps to add about 20 cm of thin, insulated, multi strand wire to each leg of the component.
Make sure to insulate any bare metal. The best way to do this is with short lengths of heat shrink wrap.
Many components have wires that are weakly soldered to the component and with use these will break off. A blob of glue (I use a glue gun) will prevent this. The small brass tabs on electric motors are particularly prone to this.
When connecting crocodile clips to the edge connector strip, push one jaw through the hole. This prevents the clip from sliding along the strip and causing a short circuit.
4 mm plugs are the best way to connect components. Find ones with stacking plugs as it is often necessary to make two or more connections to the same pin on the micro:bit (as shown on the right|).
If you can afford them, it is a good idea to buy components with 4 mm terminals so that leads can be easily attached and removed. Some schools will have components, like the one illustrated, that are used for circuit experiments in science. Borrow these as they should work (motors and lamps excluded) on the 3 volt supply from the micro:bit.
It is possible to purchase components with a length of wire and 4 mm plugs already connected to them. These are more expensive but certainly more convenient.
Contact the Data Harvest Group Ltd
N.B. The green plugs indicate that polarity is not important.
Spring connectors are a quick and simple way of connecting wires to 4 mm terminals (see picture and video below).
Note that to connect the limiting resistor to the LED, the wires have simply been twisted together.
If time and expertise is available, I would always recommend soldering wire onto components. This not an activity for primary school children but you may have a parent who is handy with a soldering iron and would be willing to solder up the components for your lessons and to apply heat shrink to insulate them.
Post a request in your school's newsletter (mine were all done for me by a willing electrician who was delighted to help out).
Bluetooth
Use the link below to access advice from the pxt.microbit website on using Bluetooth with the microbit.
https://pxt.microbit.org/reference/bluetooth/bluetooth-pairing
Smartphone apps and the micro:bit
In the eyes of my pupils, connecting with smartphone apps via Bluetooth is one of the coolest things that you can do with a micro:bit.
Follow this link for an awesome demo of the microbits Bluetooth capabilities.