Tuesday, September 22, 2026

DOST-SEI Mechanical Reasoning Reviewer: Electrical Systems & Circuits

TEACHER ABI · DOST-SEI MECHANICAL REASONING

Electrical Systems & Circuits

Trace the path first. Then decide what happens to current, voltage, resistance, and bulb behavior when a circuit changes.

5–10 minute lesson27 original questionsCircuit reasoningSaves progress

Your reviewer status

Start with the five-form Skill Check.
QUICK REVIEW

Trace the complete conducting path

BRANCH ABRANCH B
Closed vs open
Current needs a complete conducting path.
Series
One path; the same current passes through each series component.
Parallel
Separate branches provide separate paths.
Voltage
Potential difference drives charge through a circuit.
Resistance
At fixed voltage, greater resistance means smaller current: I = V/R.
Bulb failures
Retrace which complete paths remain after the failure.
DO IT FAST

PATH → BRANCH → CHANGE

PATH: is the loop complete? BRANCH: is the component on the only path or one of several paths? CHANGE: after a switch, bulb, or resistor changes, retrace the remaining circuit.

WORKED EXAMPLES

Five circuit relationships

Open switch: breaking the only path stops current in that loop.

Series bulbs: identical bulbs in one path carry the same current.

Parallel bulbs: opening one branch need not stop another intact branch.

Ohm's law: at fixed voltage, doubling resistance halves current.

Failure tracing: never assume one broken bulb turns everything off; inspect the topology first.

Common traps

Current is not “used up” by the first series component. A battery supplies potential difference, not a fixed current for every circuit. Parallel branches are not the same as extra components in series. For failure questions, redraw the remaining conducting paths.

FIVE-FORM SKILL CHECK

Can you transfer the idea across five forms?

This diagnoses your next practice step; it does not verify mastery.

CHOOSE YOUR PRACTICE

Practice at the level you need

FRESH MASTERY CHECK

Verify the competency

Mastery requires 5/5. An unsuccessful attempt loads a different set.

FAQ

Quick clarifications

Does current get used up by the first bulb?
No. In a steady series loop, the same current passes through each component.

If one bulb fails, do all bulbs always go out?
No. It depends on whether the failure breaks the only path or just one parallel branch.

Why is this Mechanical Reasoning?
DOST's own Mechanical Reasoning description explicitly includes electrical problems.

RELATED COMPETENCIES

Mechanical Reasoning sequence complete

Gears & Gear Trains · Belts, Chains, Racks & Connected Wheels · Levers, Torque & Balance · Pulleys & Mechanical Advantage · Wheels, Axles & Rotational Systems · Forces, Friction & Equilibrium · Motion, Energy & Mechanical Relationships · Fluids, Pressure & Hydraulic Systems · Heat, Sound & Everyday Physical Effects · Electrical Systems & Circuits

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