Magnets and Electromagnets | VHI Tech Lab

⚙️ Configurations

Magnetic Source Type

Magnet Strength

%

Allowed range: 10% to 100%

Selected Strength: 75%

Number of Loops (N)

turns

Allowed range: 1 to 4 turns

Coil Turns: 3 turns

DC Battery Voltage (V)

V

Allowed range: -10.00 V to +10.00 V

Selected Voltage: 5.00 V

AC Peak Voltage (V₀)

V

Allowed range: 1.00 V to 10.00 V

AC Frequency (f)

Hz

Allowed range: 0.10 Hz to 5.00 Hz

Core Material (μᵣ)

Iron core provides 50× magnetic amplification.

🧭 Laboratory Play Area

Field Grid (Arrows) Compass Field Meter Earth Background Electrons

B-Field: 35.4 G

📋 Observation Data Logger

#	Source	Loops (N)	Current I (A)	Core (μᵣ)	Probe Distance (cm)	Field B (G)	Angle θ (°)

📊 Live Measurements & Readings

Total Magnetic Field (B) 35.4 G

3540.0 μT (0.00354 T)

Horizontal Field (Bₓ) 32.1 G

Vertical Field (Bᵧ) 14.8 G

Field Vector Angle (θ) 24.7°

Circuit Current (I) 2.50 A

🧮 Live Physics Derivation

Governing Equation:

B = μ₀ · μᵣ · (N / L) · I

Live Numerical Substitution:

B = (4π×10⁻⁷ × 50 × 3 / 0.10) × 2.50 = 35.4 G

What is Magnetism & Electromagnetism?

A permanent bar magnet creates a static magnetic field due to aligned microscopic atomic electron spins within ferromagnetic domains. Field lines emerge from the North (N) pole and enter the South (S) pole.

An electromagnet creates a magnetic field when electric current flows through coiled wire loops (solenoid), as discovered by Hans Christian Oersted in 1820. Unlike permanent magnets, electromagnets can be turned on/off, have adjustable strength, and can flip polarity instantly by reversing current.

🌟 Core Learning Goals:

Understand how magnetic field vectors point away from North poles and toward South poles.
Observe how number of loops (N) and current (I) linearly scale the solenoid magnetic field (B ∝ N·I).
Witness the dramatic 50× amplification achieved by inserting a ferromagnetic Soft Iron Core (μᵣ = 50).
Use a compass to discover Right-Hand Grip Rule and track alternating AC magnetic oscillations.

Key Scientific Formulas

1. Magnetic Field of a Solenoid (Ampere's Law):
B = μ₀ · μᵣ · n · I = μ₀ · μᵣ · (N / L) · I
Where μ₀ = 4π × 10⁻⁷ T·m/A, μᵣ is relative permeability, n = N/L is turns per meter.

2. Magnetic Dipole Field on Axial Line (Bar Magnet):
B_axis = (μ₀ / 4π) · (2M / r³)
Where M is the magnetic dipole moment and r is the distance from center.

3. Magnetic Dipole Field on Equatorial Line:
B_eq = (μ₀ / 4π) · (M / r³)

4. Lorentz Force on Moving Charged Particle:
F = q · v · B · sin(θ)

5. Magnetic Flux through Surface:
Φ = B · A · cos(θ) (in Weber, Wb)

Interactive Laboratory Controls

Drag Objects: Click and drag the Bar Magnet / Electromagnet, the Compass, or the Field Meter anywhere in the play area.
Source Mode: Toggle between Permanent Bar Magnet, DC Battery Electromagnet, and AC Alternator Electromagnet in the left panel.
Flip Polarity: Click 🔄 Flip Polarity to reverse poles or invert the DC voltage sign.
Bottom Toggles: Show or hide the Field Vector Arrows, Compass needle, Digital Field Meter, and Earth Geographic/Magnetic overlay.

Key Physics Experiments

Inverse Cube Law (Dipole B ∝ 1/r³): Drag the Field Meter along the magnet axis at distances 10 cm, 20 cm, and 30 cm. Notice field drops by (1/2)³ = 1/8 and (1/3)³ = 1/27!
Testing Turns Dependency (B ∝ N): Switch to DC Electromagnet. Keep voltage fixed at 5 V and increment loops from 1 to 4. Observe exact proportional scaling of B.
Soft Iron Core Amplification: Compare the field of an Air Core (μᵣ = 1.0) with a Soft Iron Core (μᵣ = 50.0). Record rows in the Data Logger to calculate amplification factor.
AC Magnetic Reversal: Switch to AC Electromagnet, set frequency to 0.5 Hz, and watch the compass needle swing smoothly back and forth as the magnetic field oscillates.

Frequently Asked Questions

Q: Why does the compass North pole point towards Earth's North?
Earth behaves like a giant bar magnet whose magnetic South pole is geographically near the North Pole. Opposites attract, so the North pole of the compass needle points to geographic North.

Q: What is the unit relationship between Gauss and Tesla?
1 Tesla (T) = 10,000 Gauss (G). Therefore, 1 Gauss = 100 microTesla (μT) = 10⁻⁴ T.

Q: Why do magnetic field lines never cross?
At any point in space, the net magnetic field has only one resultant vector direction. If two lines crossed, a compass needle at the intersection would have to point in two directions at once, which is physically impossible.