Electric Circuit
An electric circuit is a closed path in which current can flow. It typically includes a source (e.g. battery), conductors, and loads (e.g. resistors, lamps).
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What is an electric circuit?
An electric circuit is a closed conducting path through which electric charge can flow. A simple circuit has a source of electromotive force (e.g. battery), connecting wires, and one or more loads (resistors, lamps, etc.). Current flows when the circuit is complete; opening a switch breaks the path and stops the current.
Series and parallel connections
In a series circuit, components are connected one after another; the same current flows through each. In parallel, components are connected across the same two points; the potential difference across each is the same, and currents add. Real circuits often combine both.
Circuit analysis
Kirchhoff's laws and Ohm's law allow us to find currents and voltages. In series, R_total = R₁ + R₂ + … and I is the same everywhere. In parallel, 1/R_total = 1/R₁ + 1/R₂ + … and V is the same across each branch.
In a parallel branch, why is the current through each resistor different (in general) even though the voltage across each is the same?