When is the greatest directive horizontal...

🔍 Key Concepts

• Directive horizontal force on a magnetic compass is produced by the horizontal component of the Earth’s magnetic field • The Earth’s magnetic field has both horizontal and vertical components that change with latitude (from equator toward poles) • Terms like variation and alignment with the meridian affect compass direction, not the strength of the horizontal field

💭 Think About

• Think about where on Earth the horizontal component of the magnetic field is strongest: near the magnetic equator or near the magnetic poles? • How does the inclination (dip) of the Earth’s magnetic field lines change from equator to poles, and what does that do to the horizontal component? • Do changes in variation or how well the compass needle lines up with the meridian actually change the strength of the Earth’s field, or just the direction the compass points relative to true north?

✅ Before You Answer

• Identify which answer choice relates directly to the strength of the horizontal component of the Earth’s magnetic field, not its direction • Eliminate options that deal mainly with variation (difference between true and magnetic north) instead of field strength • Ask: in which listed situation would the compass feel the strongest horizontal pull from Earth’s magnetic field lines?

When is the greatest directive horizontal force exerted on the magnetic compass of a vessel?

When the vessel is near the magnetic equator

When the vessel is near the magnetic poles

When the compass needles are nearly in line with the meridian

When the variation is near zero

🔍 Key Concepts

💭 Think About

✅ Before You Answer