How DAA Electrical Comprehension works
The Royal Navy lists the scope as electrical principles and batteries, circuits and switches.
Some questions are plain knowledge, such as what electric current is or which material conducts worst. Others show a circuit drawn with bulbs, a battery, switches or meters, and ask what a meter reads or which bulbs light when a switch is opened. One candidate reports many questions on the order in which to open and close switches to light particular bulbs.
How to read a circuit question
Bank time on the knowledge questions, then trace paths on the drawings:
- Answer knowledge questions in seconds. That leaves time for the drawings.
- Trace each bulb’s path from one side of the battery back to the other. A bulb lights only if its path is unbroken.
- An open switch breaks only the path it sits on. Bulbs on another parallel branch stay lit.
- In a series loop the current is the same everywhere; at a junction it splits between the branches.
- Know the common circuit symbols, so a drawing reads at a glance.
Worked example
A battery feeds bulb A on the main wire. After A, the wire splits into two parallel branches: bulb B on one, and switch S with bulb C on the other. “What happens when S is opened?”
Opening S breaks only C’s branch, so C goes out. B’s branch is still complete, and its current still flows through A, so A and B stay lit. The answer is “A and B light, C does not”.
Tips for the real Electrical Comprehension section
- Revise circuits from school physics: series and parallel, current and voltage, conductors and insulators. A candidate who sat it advises knowing circuit symbols and how a circuit diagram works.
- Redraw a confusing circuit on paper as a simple loop with branches.
- With about 41 seconds a question, pick your best answer on any drawing that takes over a minute and come back from the summary.
Practise DAA Electrical Comprehension on CogniPrep
Our Electrical Comprehension practice is 22 questions in 15 minutes, many with circuit drawings, with five options, a visible clock and a summary before you submit. Each sitting draws 22 from a larger bank of our own questions, with no topic making up more than a quarter of the paper, and any calculation uses whole numbers. Nothing is deducted for wrong answers, and you get your mark out of 22.