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Read a battery’s plus and minus terminals as a DC voltage source. Reason through why voltage is always measured between two points, not at one point by itself.
Use what you learned in the previous lesson to solve real-world problems.
Connect current to the rate that electric charge moves through a circuit. Use amps and milliamps to describe how much electrical flow a light, motor, or phone is drawing.
Check what you understood with a short quiz.
Use resistance as the opposition that limits current in a simple circuit. Calculate one missing value with Ohm’s law: voltage, current, or resistance.
Turn current and time into charge using amp-hours and milliamp-hours. Compare two battery capacity labels and predict which can supply the same small load longer.
Separate charge capacity from stored energy by bringing voltage into the calculation. Use watt-hours to compare batteries that have different voltages but similar Ah ratings.
Calculate power from voltage and current, then connect watts to how hard a device is working. Reason through why high-power loads drain batteries faster and produce more heat.
Trace why a battery’s measured voltage drops when a load pulls current. Use the idea of internal resistance to connect voltage sag, heat, and high-current limits.
Read common battery and charger labels such as nominal voltage, capacity, energy, input, output, and maximum current. Decide which numbers describe stored energy and which describe safe delivery rate.
Predict what changes when cells are connected in series or in parallel. Recognize that series raises voltage, while parallel raises available capacity and current-sharing ability.
Measure voltage across a battery, current through a circuit, and resistance only on unpowered parts. Choose the right meter connection so the measurement does not short the battery or damage the meter.
Review this chapter with practice based on your mistakes.
