Choose an exam and explore concepts through visual explanations, topic maps and revision checks. Open the full chapter notes whenever you need more detail.
THE VISUAL LEARNING STUDIO
See the idea. Understand the connection.
35 visual explanations across 29 chapters, with topic maps throughout the library.
The chapter index will grow as additional notes are prepared. Chapters shown here are a learning collection, not a claim that the entire exam syllabus is complete.
SEE IT. CONNECT IT. EXPLAIN IT.
Understand the chapter visually
1 visual explanation · Study the connections, then test yourself.
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COMPARE & CONNECT
Series and parallel circuits
One path · SeriesTwo branches · Parallel
1
Series
Same current through each component; Rₑq = R₁ + R₂ for two resistors.
2
Parallel
Same potential difference across branches; 1/Rₑq = 1/R₁ + 1/R₂.
3
Circuit model
Ideal wires and source; resistor values are positive and ohmic in this model.
The connection Trace whether current has one path or several branches. Compare resistor connections, not just their positions on the drawing.
Exam trap Equal branch voltage in parallel does not imply equal branch current when resistances differ.
For two equal resistors R in parallel, what is the equivalent resistance?
R/2. Their conductances add, so the equivalent resistance is smaller than either resistor.
Study the expanded notes and the credited detailed textbook lessons. The current chapter index covers core topics; it is not a claim of exhaustive coverage of every examination syllabus. Check the official syllabus and primary references.
Electricity — lesson overview
Current and resistance
Electric current is the rate of charge flow, I = ΔQ/Δt for an average. Conventional current direction is that of positive-charge flow.
Potential difference supplies an energy-per-charge comparison. Resistance relates voltage to current under specified conditions.
Ohm’s law V = IR describes an ohmic conductor with relevant physical conditions, including temperature, held suitably constant; it is not universal for every device.
Networks and power
Series resistances add: R = R₁ + R₂. For parallel branches, reciprocals add: 1/R = 1/R₁ + 1/R₂.
In series, the same current passes through successive elements; parallel branches share potential difference between their common endpoints.
Electrical power P = VI; for an ohmic resistor this can also be written I²R or V²/R under the appropriate conditions.
Worked example
Two 6 Ω resistors in parallel have equivalent resistance 3 Ω. Across 12 V, total current is 4 A, with 2 A in each identical branch.
Total power is 12 × 4 = 48 W. A circuit’s equivalent resistance does not equal the sum of parallel resistances.
A fuse or circuit breaker protects against excessive current under its designed conditions; an earth connection serves a different safety role.
