DAA Electrical Comprehension: A Complete Guide

The Electrical Comprehension section of the Defence Aptitude Assessment (DAA) checks whether you understand how simple electrical circuits and components behave. You do not need to be an electrician, but you should be comfortable with a handful of core rules. This guide walks through everything the section tests, in plain English, so you can answer confidently and quickly under time pressure.

What Electrical Comprehension tests

The section presents diagrams and short questions about basic circuits: cells (batteries), bulbs, resistors, switches and wires. You will be asked to predict what happens when something changes, such as a bulb being removed or a switch being opened. The maths is light, and most questions reward a solid grasp of a few dependable rules rather than complex calculation.

Core topics and the rules you need

Series circuits

A series circuit has just one path for the current to follow. Because everything sits on that single loop, the behaviour is predictable:

• If you remove or break one bulb, the circuit is broken and all the other bulbs go out.
• Adding more bulbs in series makes each bulb dimmer, because the supply voltage is shared between more components.
• The current is the same everywhere in a series circuit.
• The supply voltage is shared between the components on the loop.

Parallel circuits

A parallel circuit gives each component its own branch, so there is more than one path for the current:

• Removing or breaking one bulb leaves the others still lit, because their branches are unaffected.
• Each branch receives the full supply voltage, so bulbs in parallel stay at their normal brightness.

A quick way to remember it: series bulbs rely on each other, while parallel bulbs are independent.

Switches

A switch simply opens or closes the path. When a switch is open, the circuit is broken and no current flows, so the component is off. When a switch is closed, current can flow and the component is on.

Ohm's law

Ohm's law links the three key quantities: current = voltage ÷ resistance. Two simple takeaways follow from this:

• More resistance means less current (for the same voltage).
• More voltage means more current (for the same resistance).

Cells, units, conductors and fuses

A few more facts round out the section:

• Cells in series add their voltages. For example, two 1.5 V cells connected in series give 3 V.
• Units: the volt measures voltage, the amp measures current, the ohm measures resistance, and the watt measures power.
• Conductors vs insulators: materials such as copper conduct electricity, while rubber and plastic act as insulators.
• Fuses: a fuse contains a thin wire that melts if the current gets too high, breaking the circuit to protect it.

Worked example

Suppose a 12 V supply is connected across a single 4 Ω resistor. Using Ohm's law, current = voltage ÷ resistance = 12 ÷ 4 = 3 A. If you doubled the resistance to 8 Ω, the current would halve to 1.5 A, showing how more resistance means less current for the same voltage.

Tips for the Electrical Comprehension section

• Learn series versus parallel behaviour cold. Many questions turn on knowing what happens when a bulb is removed, so drill this until it is automatic.
• Memorise the units. Volt, amp, ohm and watt come up often, and quick recall saves valuable seconds.
• Use Ohm's law. Keep current = voltage ÷ resistance in mind for any question involving numbers.
• Read the diagram carefully. Check where switches sit and whether components share a path before you answer.

How to practise

The best preparation is repetition with worked feedback. Try our electrical comprehension practice to build speed and accuracy on the exact question styles. For a wider revision plan, read how to prepare for the DAA, and see the DAA explained for an overview of every section.

Please note: Forces Ready is an independent practice resource and is not affiliated with, endorsed by, or connected to the RAF, the Royal Navy or the Ministry of Defence.