Key content: electronics and switches

Examiners flag confusion over size prefixes, especially for capacitance (pF, nF, uF) where the micro symbol is often unrecognised, and reading a time axis in milliseconds. The fixed ladder is pico, nano, micro, milli, unit, kilo, mega, so 1000 pF = 1 nF and 1000 ohm = 1 kilohm. Two slips lose marks: converting the wrong way, and a bare number with no unit.

In a series circuit there is one path: current is the same everywhere and voltage is shared, so one break stops everything. In a parallel circuit each branch gets the full supply voltage and the branch currents add, so if one lamp fails the others stay lit. Candidates often reverse this; decide how many paths there are first.

Switch questions are marked on precise vocabulary. A toggle is credited for locking or latching in position, not just turning something on. A PTM makes contact only while pressed (a doorbell); a PTB breaks only while pressed. Abbreviations must be exact, e.g. SPDT. Writing only that a switch turns on and off, without naming the type and its action, misses the marks.

A reversed definition: thinking a good conductor has high resistance. It is the opposite. A conductor (copper, aluminium, carbon) has low resistance and lets current flow; an insulator (PVC, rubber, glass) has very high resistance and blocks current. That is why a cable's cores are copper and its sheath is PVC. Anchor each term to an example before answering.

On a circuit diagram, crossing wires are connected only if there is a junction dot. A dot means the wires are joined; no dot means they cross over and are NOT connected. Misreading this changes the whole circuit -- a missing or extra dot turns a real join into an unconnected crossing or the reverse. Add a dot only where you intend a join, and read each path by its dots.

A diode and an LED conduct in one direction only, so the symbol must face the right way -- the triangle points the way conventional current flows, into the bar. Drawn reversed, it blocks the current, the circuit fails and the orientation mark is lost. Check the supply polarity (+ to -) and point the triangle so current can flow through it in normal use.

A sharp wrong belief: that a push-to-make (PTM) button switches something on and stays on, like a toggle. It does not. A PTM is momentary and normally open -- it conducts only while held down and springs open the moment you release it. The switch that latches and stays put is the toggle. Ask whether the switch must hold its state (toggle) or act only while pressed (PTM/PTB).