Key relationship
Bcoil=μ₀NI/(2R); aligned tanθ=Bcoil/BH.
Physics · Practical apparatus
Tangent-galvanometer alignment
Align the coil plane with the magnetic meridian, then infer horizontal Earth field from the deflection. Deliberate misalignment demonstrates why the perpendicular-field condition matters.
Open the interactive experiment →Tangent-galvanometer alignment
சுருளை காந்த வடதெற்கு தளத்தில் அமைத்து கோணத்திலிருந்து பூமியின் கிடைமட்டப் புலத்தைக் கணக்கிடவும்.
Key notes, relationships and model limits
Practical tip
Align the coil plane with the magnetic meridian, then infer horizontal Earth field from the deflection. Deliberate misalignment demonstrates why the perpendicular-field condition matters.
Common trap
Zero deflection with zero current cannot determine BH by dividing0/0.
Model limits
Circular coil at compass centre; coil plane in magnetic meridian only when azimuth0. Misalignment explicitly rotates coil field and invalidates the simple tangent estimate. Earth field prescribed.
What you will learn
Read a tangent-galvanometer estimate and diagnose alignment error.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
N5,I0.2 A,R0.1 m gives Bcoil≈6.283 μT andθ≈8.93° for BH40 μT.
Why this matters
The model connects tangent-galvanometer alignment with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
The tangent law requires the two fields to be?
- Parallel
- Perpendicular
- Equal always
Read the explanation
Vector addition then gives tanθ=Bcoil/BH.
Course connection: Virtual apparatus preparation. Check exact board/exam membership in the syllabus sources. Physical practical work remains necessary.