Electrical and Electronic Fundamentals
What the domain tests
Electrical and electronic fundamentals is the language of the whole subject: charge, current, voltage, resistance, power and energy, plus the difference between analogue and digital signals. The exam expects you to define quantities, use correct units, and move confidently between a physical circuit and its mathematical model.
Core rules
- Charge Q is measured in coulombs; current I = Q/t, so one ampere is one coulomb per second. Conventional current flows from positive to negative; electron drift is opposite.
- Potential difference is energy per unit charge, V = W/Q. Emf is the source energy per unit charge; terminal voltage falls under load because of internal resistance.
- Ohm's law V = IR applies to ohmic conductors at constant temperature. Power P = VI = I²R = V²/R; energy E = Pt.
- DC has constant polarity; AC reverses periodically. Frequency f = 1/T. Malaysian mains is commonly 240 V, 50 Hz.
- Analogue signals vary continuously; digital signals use defined levels and are processed as bits.
Worked example
A 12 V battery supplies 500 mA for 3 minutes. Convert: I = 0.500 A and t = 180 s. Charge Q = It = 0.500 × 180 = 90 C. Power P = VI = 12 × 0.500 = 6.0 W. Energy E = Pt = 6.0 × 180 = 1080 J = 1.08 kJ. In ampere-hours, 90 C is 90/3600 = 0.025 Ah, a small fraction of a 2.0 Ah battery rating.
Traps that cost marks
Using minutes instead of seconds, or mA instead of A, is the most common slip. Do not confuse power (watts) with energy (joules); energy needs time. Watch the direction of conventional current, and do not quote peak voltage when the question asks for RMS. Internal resistance reduces terminal voltage only when current flows.