IAN LANG ELECTRONICS

GCSE Electronics

GCSE Electronics is a very new qualification offered in England and Wales and first began to be taught in 2009, with last year being the first examination paper. I've managed to get hold o a copy of the specimen and I must say, for an entry level qualification, it does get shockingly hard in places. With this in mind, I've gone through it and given answers and underneath the answers I've given a reason for that answer.

Those of you not doing GCSE but who are trying to find your feet in Electronics will get some benefit from this too, as some of these questions are ones that beginners and hobbyists are always pondering. So without further ado, let's leap in and get the exam done. There's two question papers, we'll start with E1, Discovering Electronics. Click the link left for paper 2, Applications of Electronics.

Solenoid

Light Sensor

Latch

There's lessons to be learned in terminology here. An input is when the circuit is affected by outside influences; this could be temperature, light, movement , magnetism, in fact anything that can be sensed or measured or even somebody pressing a button. An output is something that the circuit does by itself either automatically or as a result of an input.
Therefore, wherever you see the term "sensor" it's an input. It could be a gas sensor, a magnetic sensor, a humidity sensor or any of dozens. If it's a sensor it's an input.

A solenoid is activated by electro-magnetism. Your circuit provides the electricity to power the magnet. It might do it once every so many seconds without an input, or it could do it when a button is pressed. It doesn't matter how or why it does it, it's the circuit that's doing it. And so it's an output.

When you are doing this or any other kind of exam, look out for tricks. Examiners are your enemy and love to catch you out on points of hair-splitting. It's tempting to say the answer to the last bit is a time delay. In an abstract way you'd be right, but in actual terms you'd be wrong; the time delay could work the latch but the latch is the device that keeps the system on for a length of time. Don't let them trip you up.

LED

LDR

Resistor

MOSFET

Whoa, horsey, there is a shockingly nasty trick being played here. Look at the front of the question. It says:

"Here is a list of electronic components"

It doesn't say that all the following questions will refer to that list. That's nasty, because they give you a variable resistor in that list, but a fixed resistor as a component symbol. What a bunch of !$%&*@

Another nasty one because it isn't immediately clear from how they've labelled the voltages what it is they actually want. V1 looks like between point P and 0V, which is then 0V. V2 looks like base-emitter, 0.7V and V3 collector -emitter, so that's your 6V.