Geomagnetism Lab: Dip Needle (Angle of Dip)
Investigate the **Angle of Dip ($\delta$)**—the angle between the Earth's total magnetic field ($\text{B}_E$) and the horizontal. This crucial quantity varies with latitude and is measured by the **Dip Needle**.
Key Equations & Concepts
▼The relationship between the horizontal ($\text{B}_H$) and vertical ($\text{B}_V$) components of the Earth's magnetic field is: $$ \tan\delta = \frac{\text{B}_V}{\text{B}_H} $$
Total Field: $$ \text{B}_E = \sqrt{\text{B}_H^2 + \text{B}_V^2} $$
- **Magnetic Equator ($\delta=0^\circ$):** $\text{B}_V = 0$ (Needle is horizontal).
- **Magnetic Poles ($\delta=90^\circ$):** $\text{B}_H = 0$ (Needle is vertical).
Experiment 1: Dip Angle Simulation (Changing Latitude)
Adjust the location (latitude) to observe how the Dip Needle aligns itself with the Earth's total magnetic field ($\text{B}_E$).
Ratio 0.5: Typical mid-latitude region.
Experiment 2: Total Field ($\text{B}_E$) Calculation Challenge
Calculate the **Total Magnetic Field ($\text{B}_E$)** using the given measured field components and the calculated Dip Angle ($\delta$).
At the **Magnetic Equator**, the Earth's magnetic field lines are parallel to the surface (horizontal). The Dip Needle shows $\delta = 0^\circ$ because there is no vertical component ($\text{B}_V = 0$).
Earth's Field & Declination (11th/12th Std)
The **Angle of Declination** is the angle between the **Geographic Meridian** (true north) and the **Magnetic Meridian** (magnetic north). This angle is also a key element of the Earth's magnetic field description.
The total field $\text{B}_E$ is the vector sum of its components. Calculating $\text{B}_E$ requires the Pythagorean theorem, just like finding the magnitude of any resultant vector.
Modern measurements of $\text{B}_H$ and $\text{B}_V$ are often done using sophisticated electronic **magnetometers** instead of relying on a physical needle.
