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Concept module

Basic Circuits

Keep one battery and two resistors in view while current, voltage, resistance, Ohm's law, and the contrast between series and parallel all stay tied to one honest circuit.

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Starter track

Step 3 of 60 / 6 complete

Electricity

Earlier steps still set up Basic Circuits.

1. Electric Fields2. Electric Potential3. Basic Circuits4. Power and Energy in Circuits+2 more steps

Previous step: Electric Potential.

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Why it behaves this way

Explanation

A basic circuit needs only a source of voltage, a path for charge to move, and resistance that limits how much current the source can drive. Ohm's law connects those three ideas with one compact rule: more voltage pushes more current, and more resistance holds that current back.

This module stays intentionally bounded. One battery drives two resistors, and the only topology change is whether those resistors sit in one series loop or in two parallel branches. That is enough to teach current, voltage, equivalent resistance, and the intuition behind Ohm's law without turning the page into an electronics workbench.

Key ideas

01For one fixed circuit, Ohm's law means current scales linearly with voltage and inversely with equivalent resistance.

02In series, the same current flows through every resistor because there is only one loop, so resistances add and the source voltage is shared across the resistors.

03In parallel, each branch sees the full battery voltage, so branch currents depend on branch resistance and the total current is the sum of those branch currents.

Frozen walkthrough

Step through the frozen example

Frozen walkthrough

Solve the circuit that is on screen right now. The same battery value, resistor values, and topology drive the stage, the readout card, the overlays, and the graphs.

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Frozen valuesUsing frozen parameters

For the current circuit, what one-number equivalent resistance does the battery feel, and what total current follows from that load?

V

Battery voltage

12 V

R_{A}

Resistor A

6 ohm

R_{B}

Resistor B

6 ohm

1. Start with the live topology

This setup uses series loop, so

R_{eq} = R_{A} + R_{B}

2. Substitute the resistor values now on screen

With

R_{A} = 6

and

R_{B} = 6

R_{eq} = 6 + 6

, so

R_{eq} = 12

3. Use Ohm's law on the whole circuit

I_{total} = \frac{V}{R _{eq}} = \frac{1}{2} 12

4. Compute the total current

That gives

I_{total} = 1

Equivalent resistance and total current

R_{eq} = 12, I_{total} = 1

Series resistances add directly, so each extra ohm raises the one-number load and reduces the same loop current everywhere.

Current-split checkpoint

Use the matched-resistor presets. Why does the total current become larger in the parallel circuit than in the series circuit even though the same battery and the same two resistors are still present?

Make a prediction before you reveal the next step.

Predict whether the battery is seeing more resistance or less resistance before you switch the topology.

Check your reasoning against the live bench.

The parallel circuit gives the battery a smaller equivalent resistance because the charge has two paths instead of one long path. With the same battery voltage, Ohm's law then gives a larger total current.

Series adds resistances directly, so two 6 ohm resistors become 12 ohm. Parallel combines them into 3 ohm, which is a much lighter load on the same battery. Lower equivalent resistance means higher total current.

Common misconception

Current gets used up by the first resistor, so less current reaches the second resistor in a series loop.

Current is the rate of charge flow through one continuous loop. In a steady series circuit, the same amount of charge per second passes every point in that loop.

What changes across a resistor is voltage, not the amount of current that remains. The resistor creates a voltage drop while the loop current stays the same.

Quick test

Reasoning

Question 1 of 5

Answer from the live circuit logic, not from detached rules. Each question asks what the stage, readout, or graphs must mean.

A battery drives two resistors in one steady series loop. Which statement about the current is correct?

Use the live bench to test the result before moving on.

Accessibility

The simulation shows one battery on the left and two resistor blocks arranged either in one series loop or in two parallel branches. A readout card on the right reports the live battery voltage, resistor values, equivalent resistance, total current, branch currents, and branch voltages.

Optional overlays add current arrows on the wires, voltage labels on the battery and resistors, and node markers that show when two branches share the same top and bottom nodes. Compare mode adds a dashed ghost circuit for the second setup so topology or resistor changes stay visible without changing the main stage.

The stage is intentionally bounded to one battery and two resistors. There are no capacitors, switches, or symbolic solvers, so every displayed change stays tied to the same beginner-friendly current, voltage, and resistance logic.

Graph summary

The Ohm's law current map plots total current, branch A current, and branch B current against battery voltage for the current resistor setup and topology. Hovering the graph previews a different battery voltage on the stage without changing the actual controls.

The voltage-share graph sweeps only resistor B while holding the battery and resistor A fixed. In series it shows how the source voltage is divided, and in parallel it shows that both branches stay pinned to the full battery voltage even as the branch currents differ.

Keep the electricity story moving

Keep this idea moving

Open the next concept, route, or track only when you want the current model to widen into a larger branch.

See rate and total in the same loopElectricity