Circuit Lab — Interactive Schematic & DC Simulator

How an electric circuit works

An electric circuit is a closed loop that lets charge flow. A voltage source — a battery or supply — pushes charge around the loop, and the components along the way resist, store, or use that energy. Current is the rate of charge flow, voltage is the energy given to each unit of charge, and resistance is how strongly a component opposes the flow. For any current to flow, the loop must be complete; break it with an open switch and everything stops.

This simulator solves circuits the way engineers do: nodal analysis. It treats each junction (node) as a point with an unknown voltage, applies the rule that current in must equal current out at every node, and solves the resulting equations for the whole circuit at once. That is why it can report the voltage, current, and power at every component the instant you press Simulate.

Experiments to try in this simulation

1. Ohm's law directly: build a battery and a single resistor, then change the resistance. Current falls as resistance rises, exactly in proportion — double the resistance and the current halves.

2. Series versus parallel: wire two resistors in series and note the total, then rewire them in parallel. Series resistances add; parallel ones combine to less than either alone. Watch how the current splits between parallel branches.

3. A switch controls the loop: add a switch and open it. All current stops, because an open switch breaks the complete path a circuit needs.

4. Follow the power: read the milliwatts each component dissipates. Add them up and they equal the power the source delivers — energy is conserved, exactly as it must be.

Key laws

Two laws run every circuit here. Ohm's law, V = IR, ties the voltage across a component to the current through it and its resistance. Kirchhoff's laws add the bookkeeping: the current law says the currents into any node sum to the currents out (charge is conserved), and the voltage law says the voltage changes around any loop sum to zero (energy is conserved).

Nodal analysis is simply these laws applied systematically. The power dissipated in a resistor is P = IV = I²R, which is why resistors warm up and why the simulator can show milliwatts per component. Together these relationships let you predict any DC circuit before you build it.

Real-world applications

Every electronic device — from a phone charger to a car's wiring to a data centre — is designed with exactly these principles. Engineers use nodal analysis (usually inside software like SPICE) to predict how a circuit behaves before committing it to hardware, saving the cost of building and testing physical prototypes. Series and parallel resistance, Ohm's law, and power dissipation are the foundation of electronics, and the DC analysis you practice here is the first step toward AC circuits, filters, and the analog design that underlies all modern technology.