🔄 The Complete Energy Chain

Battery → Current → Magnetic Field → Motor → Motion

Energy Conversion in an RC Car

When you power on your RC car, a chain of energy transformations occurs. This page connects everything you've learned in the Chemistry and Physics pages, showing how chemical reactions in a simple AA battery result in mechanical motion.

The Four-Stage Energy Chain

Each stage represents a different type of energy transformation.

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1. Chemical Energy

What happens: Inside the battery, zinc atoms lose electrons (oxidation) while manganese dioxide gains them (reduction). This redox reaction releases energy stored in chemical bonds.

net reaction:
Zn(s) + 2MnO2(s) → ZnO(s) + Mn2 O3(s)

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2. Electrical Energy

What happens: The electrons released by the chemical reaction flow through the external circuit as electric current. The battery's voltage (1.5V per cell) pushes these electrons through the wires.

I = V / R (Ohm's Law)

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3. Magnetic Energy

What happens: When current flows through the motor's coiled wire, it creates a magnetic field (right-hand rule). This field interacts with the permanent magnets in the motor.

B = μ₀ × N × I / L

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4. Mechanical Energy

What happens: The magnetic forces create torque on the motor armature, causing it to spin. This rotation transfers through gears to the wheels, accelerating the car according to F = ma.

V_f = V_i + at, d = V_it + ½at²

Why This Matters

Every battery-powered device, from your phone to electric vehicles, follows this same basic energy chain. By understanding how each stage works and connects to the next, you directly learn about the physics and chemistry that powers modern technology. The calculations below let you explore the numbers and see how changing one variable (like battery capacity or motor current) affects the entire system.

📊 Interactive Pipeline

Step 1: Battery Chemistry

Start by calculating your battery pack's energy output.

Open Battery Calculator

No battery data loaded. Run the chemistry calculator first (stoichiometry mode).

Step 2: Motor Physics

See how the electrical energy powers the motor.

Open Motor Simulator

Motor data will appear after using the physics simulator.

Energy Flow Diagram

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Chemical Energy

-- Wh

→

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Electrical

-- V × -- A

→

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Heat Loss

I²R

→

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Mechanical

Motor motion

Energy is conserved but transformed. Some is lost as heat in battery internal resistance and motor windings.

📖 Complete Worked Example

RC Car: From Battery to Wheel

Scenario: An RC car uses a 4×AA alkaline pack (6V, 2000mAh) to power a small DC motor (3Ω, 50-turn coil).

Part A: Battery Chemistry

Pack voltage: 4 × 1.5V = 6.0V
Pack capacity: 2000 mAh
Total charge: 2000 × 3.6 = 7200 C
Total energy: 6.0V × 7200C = 43,200 J = 12.0 Wh

Part B: Current Flow

Internal resistance: 4 × 0.3Ω = 1.2Ω
Total resistance: 3Ω + 1.2Ω = 4.2Ω
Current: 6V / 4.2Ω = 1.43 A
Loaded voltage: 6V - (1.43A × 1.2Ω) = 4.28V at motor

Part C: Magnetic Field in Motor Coil

For motor coil (N=50, L=2cm, I=1.43A):
B = μ₀ × N × I / L
B = (1.257×10⁻⁶) × 50 × 1.43 / 0.02
B ≈ 4.5 mT

Note: This calculation assumes an air-core coil. In a real motor, an iron core would increase the magnetic field strength significantly, often by a factor of 1000 or more.

Part D: Power & Runtime

Power to motor: 4.28V × 1.43A = 6.1W
Power lost to heat: 1.43² × 1.2 = 2.5W
Efficiency: 6.1 / (6.1 + 2.5) ≈ 71%
Runtime: 2000mAh / 1430mA ≈ 1.4 hours

Interpretation

The battery's chemical energy is converted to electrical energy at 71% efficiency (29% lost as heat in internal resistance). The current creates a magnetic field of about 4.5mT in the motor coil, which interacts with permanent magnets to produce rotation. The car can run for approximately 1.4 hours before the batteries run out.

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