🧪 Virtual Labs & Simulations

Hands-on exploration of battery and motor concepts

💡 Did You Know?

🏎️ RC Cars Hit 200+ mph!

The fastest RC car ever recorded hit 377.73 km/h in 2025. That's faster than most supercars!

🛸 First RC: 1898

Nikola Tesla demonstrated the first radio-controlled vehicle (a boat) in 1898. At the time, people thought it was magic!

🔋 Brushless Motors Rule

Modern RC cars use brushless motors (motors that use an electronic controller to switch current to the stator windings instead of physical brushes) that are up to 90% efficient, compared to only 75% for brushed motors!

Lab 1: Battery Discharge & Internal Resistance

Objectives

  • Observe how internal resistance causes voltage drop under load
  • See how higher current draw creates greater voltage sag
  • Understand the relationship Vloaded = Vopen - (I × Rinternal)

Instructions

  1. Adjust the current draw slider and observe voltage changes
  2. Increase internal resistance and see the voltage sag increase
  3. Notice how higher current or resistance causes more power loss

Battery Pack Visualization

AA
AA
AA
AA

4×AA Battery Pack (6V nominal) — Fully Charged

Experiment: Voltage Sag Under Load

0.5 A
1.2 Ω
Open-Circuit Voltage: 6.0 V
Loaded Voltage: 5.4 V
Power Lost to Heat: 0.3 W

Learning Outcomes

  • Higher current = more voltage drop (V = IR)
  • Internal resistance causes energy loss as heat
  • Fresh batteries have lower internal resistance

Lab 2: Motor Current & Magnetic Field

Objectives

  • See how current affects magnetic field strength
  • Observe the effect of coil turns
  • Understand the relationship between magnetic field and motor speed

Controls

1.0 A
50 turns

Magnetic Field Visualization

Magnetic Field: 3.14 mT

Learning Outcomes

  • Magnetic field is proportional to current (B ∝ I): Increasing the current through the coil creates a stronger magnetic field.
  • More turns = stronger field (B ∝ N): Adding more wire turns multiplies the magnetic effect.
  • Magnetic field determines motor torque: A stronger magnetic field creates more force on the armature, producing more torque.
🔌 Back-EMF and Motor Speed Relationship ▼

Back-EMF (Electromotive Force): As a motor spins, it acts like a generator and produces a voltage that opposes the supply voltage. This is called Back-EMF.

How it Works:

  • At startup (low speed): Back-EMF is nearly zero, so full current flows and the motor produces maximum torque to accelerate.
  • As motor speeds up: Back-EMF increases, reducing the effective voltage and current. This means less torque at higher speeds.
  • At top speed: Back-EMF nearly equals the supply voltage. Current drops to just enough to overcome friction, and the motor stops accelerating.

The Relationship: Motor speed is determined by the balance between available torque (from the magnetic field) and the forces opposing motion (friction, air resistance). As the magnetic field increases, the motor can produce more torque and potentially reach higher speeds, but Back-EMF limits how efficiently this extra energy translates to speed.

Formula: Back-EMF ∝ Speed × Magnetic Field Strength

🚗 Virtual RC Car Simulator

See your battery power in action! Control the throttle and watch the car accelerate based on real physics calculations.

Side View Animation

Shows forces, speed, and battery level

Race Track (Top View)

Oval track with lap timing

Controls

Kinematics Calculations (F = ma)

Motor Force (F): 0.000 N
Acceleration (a): 0.000 m/s²
Velocity (v): 0.00 m/s
Power (P = VI): 0.00 W

Note: All displayed values are rounded to three decimal places for visual stability during real-time calculations.
Please pause the simulation to see accurate values if they are flickering.

📐 Physics Formulas Used ▼

Newton's 2nd Law

F = m × a
a = Fnet / m

The net force on the car determines its acceleration. More force = faster acceleration.

Motor Force (Internal Torque)

Fmotor = τ / r
τ = torque, r = wheel radius

The motor's internal torque is converted to a pushing force at the wheels. This force decreases as speed increases due to Back-EMF.

Friction Force

f = μ × N = μ × m × g
(opposes motion)

Friction always opposes motion and increases with the car's mass.

Kinematics

v = v₀ + at
x = x₀ + vt

These equations describe how position and velocity change over time.

Understanding Force Balance (Why the Car Reaches Top Speed)

At Startup (Low Speed): The motor pushes with maximum force (e.g., 3.5 N). Since friction is small compared to motor force, the car accelerates quickly.

As Speed Increases: Back-EMF reduces the motor's effective current, decreasing motor force. Meanwhile, the friction force stays relatively constant.

At Top Speed: Motor force drops to match friction force exactly. For example:

Motor Force = 0.49 N
Friction Force = 0.49 N
Net Force = 0.49 - 0.49 = 0.00 N
Acceleration = 0.00 m/s²

At this equilibrium, the car maintains constant speed without accelerating. The power being used (P = F × v) stays within the battery's limits.

🔬 Extra Experiments

Experiment A: Efficiency Challenge

Using the battery calculator, find the combination of battery configuration and motor resistance that gives the best efficiency (most power to motor, least power lost to heat).

Start Experiment

Experiment B: Runtime Prediction

Calculate the expected runtime for different current draws. Then compare theoretical vs. typical real-world values.

Start Experiment

Experiment C: Series vs. Parallel

Compare a 4×AA series pack vs. a 2S2P (2 series, 2 parallel) configuration. How do voltage, capacity, and internal resistance differ?

Start Experiment

Experiment D: Material Effects

In the motor simulator, compare magnetic field strength with air core vs. ferrite core. How much does it increase?

Start Experiment
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