Electrical Theory I: DC Circuits

What you'll learn

• Define charge, current, voltage, resistance, power and energy with their units and prefixes, and explain the effects of current on the human body
• Describe how friction, chemical action, magnetism, light, heat and pressure produce electricity, and distinguish DC from AC sources
• Apply Ohm's law and the power equations to loads, wrong-voltage operation, conductor heating, continuous loads, efficiency and temperature effects
• Calculate resistance from resistivity and temperature, read resistor markings, and choose resistors by value, tolerance and power rating
• Solve series, parallel and combination circuits, apply Kirchhoff's laws, and predict the effects of opens and shorts
• Analyze loaded dividers, bridges, sources with internal resistance, multi-source circuits and three-wire systems with open neutrals
• Use multimeters, clamp meters and insulation testers correctly, interpret accuracy and misleading readings, choose meters by CAT rating, and prove circuits dead with live–dead–live
• Size battery banks from cells in series and parallel, and explain charging, hazards, testing and DC power systems
• Explain magnetic fields, electromagnets, relays, motor force and electromagnetic induction
• Calculate RC and RL time constants and stored energy, and control inductive kick and stored-energy hazards
• Calculate conductor resistance and voltage drop, check them against code limits, and choose conductor sizes for distance and load
• Explain how fuses and breakers protect circuits, check interrupting ratings, and troubleshoot DC circuits systematically