WattsUp 3lite Education
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Interactive Physics

WattsUp

Learn how circuits work — explore Ohm's Law, series & parallel circuits, power, voltage dividers, and more. Build your own and test it with a real backend simulation engine.

Lesson 01 — Basics

What is a Circuit?

A circuit is a closed loop that allows electric current to flow. It needs a power source, a conductive path, and a load to do useful work.

9V
🔋Power SourceProvides EMF (e.g. battery)
〰️ConductorCarries current (wire)
💡LoadConverts energy (bulb, etc.)
🔄Closed LoopCurrent must have a complete path

Lesson 02 — Ohm's Law

Ohm's Law

The relationship between voltage, current, and resistance — the foundation of all circuit analysis.

V = I × R
I = V / RR = V / I
9 V
100 Ω
0.09
Current (A)
90
Current (mA)
0.81
Power (W)

Lesson 03 — Series

Series Circuits

In a series circuit, components are connected end-to-end in a single path. The same current flows through every component.

R1 R2 R3
Same ICurrent is identical through every component
V addsV₁ + V₂ + V₃ = Vsupply
R addsRtotal = R₁ + R₂ + R₃

Lesson 04 — Parallel

Parallel Circuits

In a parallel circuit, components share the same two nodes. Each branch has the same voltage but can carry different currents.

R1 R2 R3
Same VVoltage is identical across every branch
I addsItotal = I₁ + I₂ + I₃
1/R1/Rtotal = 1/R₁ + 1/R₂ + 1/R₃

Lesson 05 — Power & Energy

Electrical Power & Energy

Power is the rate of energy transfer (watts). Energy is power sustained over time — what you actually pay for on your electricity bill (kilowatt-hours).

P = V × IVoltage × Current
P = I²RCurrent² × Resistance
E = P × tPower × Time (J or kWh)
12 V
1.00 A
1.0 h
12.00
Power (W)
43200
Energy (J)
0.0120
Energy (kWh)
0 W2400 W max
💡LED Bulb — 10 WRuns 100 h on 1 kWh
🖥️Laptop — 65 W1 kWh lasts ~15 hours
🔌Kettle — 2000 WBoils in ~2 min, uses 0.07 kWh
📱Phone charger — 5 WFull charge ≈ 0.015 kWh

Lesson 06 — Voltage Divider

Voltage Divider

Two resistors in series split the supply voltage proportionally. Vout tapped between them scales with the ratio of R2 to the total resistance.

FormulaVout = Vin × R2 / (R1 + R2)
12 V
1000 Ω
1000 Ω
6.00
Vout (V)
50.0
Ratio (%)
6.00
Current (mA)
SensorsThermistors & LDRs shift Vout as temperature or light changes R2
ADC inputScale a 5V signal down to 3.3V for a microcontroller ADC pin
BiasSet a midpoint reference voltage in amplifier circuits

Lesson 07 — Electric Potential

Electric Potential

Electric potential is the electric potential energy stored per unit charge at a point. Voltage is the difference in potential between two points — it drives current to flow.

V = W / QWork per unit charge (J/C)
ΔV = Vₐ − VₙPotential difference
W = Q × VWork done moving charge Q
100 mC
12 V
1200.000
Work W (mJ)
1.20000
Work W (J)
⚡Electric PotentialEnergy per unit charge at a point — measured in Volts (J/C)
🔋EMFElectromotive force — potential difference supplied by the source
〰️EquipotentialLines of equal potential — no work needed to move charge along them
📐Ground (0 V)Potential is always measured relative to a reference point
AnalogyLike gravitational PE — charges at higher potential have more stored energy
DirectionConventional current flows from high (+) to low (−) potential
Unit1 Volt = 1 Joule per Coulomb (J/C)

Lesson 08 — Complex Networks

Equivalent Resistance

Real circuits often combine series and parallel groups in multiple layers. The key technique is progressive reduction — always start with the innermost (most nested) series or parallel group, replace it with a single equivalent resistor, then work outward until one resistor remains.

Step 1Identify the innermost series or parallel group
Step 2Replace with Req using the series or parallel formula
Step 3Repeat until only one equivalent resistor remains

Lesson 08A

( R1 ∥ R2 ) + R3

A parallel pair feeds into a series resistor — the simplest mixed topology.

( R1 ∥ R2 ) — R3
R1 R2 R3
100 Ω
100 Ω
50 Ω
100
R eq (Ω)

Lesson 08B

R1 + ( R2 ∥ (R3 + R4) )

A series resistor followed by a parallel block where one branch itself contains two series resistors — 3-level reduction.

R1 — [ R2 ∥ (R3+R4) ]
R1 R2 R3 R4
30 Ω
120 Ω
60 Ω
60 Ω
90
R eq (Ω)

Lesson 08C

(R1 + R2) ∥ (R3 + R4)

Two parallel branches, each containing two series resistors — reduce each branch first, then combine in parallel.

( R1+R2 ) ∥ ( R3+R4 )
R1 R2 R3 R4
100 Ω
100 Ω
100 Ω
100 Ω
100
R eq (Ω)

Circuit Lab

Simulation Lab

Configure a circuit and simulate — results come from the backend calculation engine.

Series
Parallel
Mixed
Builder

Series Circuit

9 V
100 Ω
200 Ω
150 Ω