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Magnetic Fields

Magnetic Fields

A moving charge or a current creates a magnetic field in the surrounding space, in addition to its electric field. The magnetic field exerts a force on any other moving charge or current that is present in the field. Like an electric field, the magnetic field is also a vector field. At any position, the direction of the magnetic field is defined as the direction in which the north pole of a compass needle points.
A magnetic field is defined by the force that a charged particle experiences...

Magnetic Field Lines

Magnetic Field Lines

The representation of magnetic fields by magnetic field lines is very useful in visualizing the strength and direction of the magnetic field. Each of the magnetic field lines forms a closed loop. The field lines emerge from the north pole (N), loop around to the south pole (S), and continue through the bar magnet back to the north pole.
Magnetic field lines follow several hard-and-fast rules:

Meridians

Meridians

In surveying, meridians are vital reference lines to measure directions and establish accurate land orientations. Meridians run from the north to the south poles, providing a stable framework for angular measurements and mapping. Meridians are fundamental in survey design, with the primary types being astronomic, magnetic, and assumed meridians. Each type offers distinct benefits and limitations, selected based on the project's scale and precision needs.The astronomic meridian is aligned with...

Compass

Compass

The compass is a fundamental instrument that operates by aligning its magnetic needle with Earth's magnetic field. This alignment facilitates navigation and orientation, offering a means to determine direction relative to magnetic north. However, the magnetic needle points to magnetic north, which differs slightly from true geographic north due to magnetic declination, which is the angular deviation between these two points. Declination varies based on geographic location and shifts over time...

Magnetic Declination

Magnetic Declination

Magnetic declination is the angle between true north, which aligns with the Earth's rotational axis, and magnetic north, which follows the direction of the Earth's magnetic field. This discrepancy exists because the magnetic poles do not coincide with the geographic poles. The value of magnetic declination depends on the observer's location on Earth and is subject to changes over time due to the dynamic nature of the Earth's magnetic field.The declination is called eastern when magnetic north...

Local Attraction

Local Attraction

Local attraction refers to disturbances in compass readings caused by magnetic influences from nearby objects such as metal fences, buried pipes, vehicles, buildings, power lines, or natural iron ore deposits. Small items like wristwatches, steel tools, or belt buckles can also interfere with the compass by creating local magnetic fields that distort the Earth's natural magnetic field. These distortions lead to inaccurate readings, posing navigation and land surveying challenges.Local...

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Related Experiment Video

Updated: May 25, 2026

Remote Magnetic Navigation for Accurate, Real-time Catheter Positioning and Ablation in Cardiac Electrophysiology Procedures

Remote Magnetic Navigation for Accurate, Real-time Catheter Positioning and Ablation in Cardiac Electrophysiology Procedures

Published on: April 21, 2013

Navigation: bat orientation using Earth's magnetic field.

Richard A Holland¹, Kasper Thorup, Maarten J Vonhof

¹Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey 08544, USA. rahollan@princeton.edu

|December 8, 2006

Summary

This summary is machine-generated.

Big brown bats (Eptesicus fuscus) use a magnetic compass for long-distance navigation. Artificially shifting Earth's magnetic field altered their homing behavior, confirming this reliance.

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Area of Science:

Zoology
Animal Behavior
Sensory Biology

Background:

Bats navigate primarily using echolocation for short-range orientation.
Long-distance navigation mechanisms in bats remain largely unknown.
Eptesicus fuscus, the big brown bat, exhibits homing behavior.

Purpose of the Study:

To investigate the sensory mechanisms underlying long-distance navigation in Eptesicus fuscus.
To determine if bats utilize a magnetic compass for homing.

Main Methods:

Experimental manipulation of the Earth's magnetic field.
Observation of homing behavior in Eptesicus fuscus under altered magnetic conditions.

Main Results:

Artificial shifts in the Earth's magnetic field significantly altered the homing behavior of big brown bats.
This demonstrates a direct link between magnetic field perception and navigation direction.

Conclusions:

Eptesicus fuscus relies on a magnetic compass for effective long-distance navigation.
This finding highlights the sophisticated sensory capabilities of bats for nocturnal navigation.