Dhristi JEE 2022-24

What is Angle of Dip?

The angle of dip is also sometimes called the magnetic dip and is defined as the angle which is made by the earth’s magnetic field lines with the horizontal.

The angle of dip usually is said it varies from point to point by providing the information which is related to the movement of the earth’s magnetic field.  The angle of dip is said to be positive when the magnetic field points in the direction that is downwards. When the magnetic field points towards upward direction then the angle of dip is said to be negative.

The angle of dip is 0° when the needle of the dip rests horizontally while the angle of dip is 90° when the needle of dip rests vertically.

When the component that is horizontal and the vertical component of the earth’s magnetic field are equal the angle of dip is equal to 45°.


Magnetic Dip

Geomagnetics is that branch of geophysics concerned with all aspects of the magnetic field which is of earth’s that is including its origin, variation through time and manifestations in the form of magnetic poles. The remnant of the magnetization of rocks and local or the regional magnetic anomalies. The latter generally reflects the difference which is between theoretical and observed magnetic intensities at points of measurement with a magnetometer. When plotted on a magnetic map, it is known as an aeromagnetic map if the magnetometer was flown across the area. The anomalies provide the basis for inferences that are about probable subsurface structure and composition.

The magnetic dip or the dip angle or the magnetic inclination is the angle made with the horizontal by the line of the earth's magnetic field. This angle generally varies at different points on the surface of the earth. The positive values of inclination indicate that the earth's magnetic field is pointing downward into the Earth that too at the point of measurement. And the value if negative indicates that it is pointing upward. The dip angle is said to be in principle the angle which is made by the needle of a vertically held compass. In practice, ordinary compass needles may be weighted against dip or may be unable to move freely in the correct plane. The value of it can be measured even more reliably with a special instrument typically called a dip circle.

In 1544 the angle which is the dip was discovered by the engineer Georg Hartmann. A method which measures it with a circle of dip was described by Robert Norman in England in 1581.


Magnetic Inclination

Magnetic dip results from the tendency of a magnet to align itself with lines of the magnetic field. As the planet's magnetic field lines are not parallel to the surface, the northern end of a compass needle will point downward. That is in the northern hemisphere it is a positive dip or upward while in the southern hemisphere it is a negative dip. The range of dip is from -90 degrees at the North Magnetic Pole to +90 degrees at the South Magnetic Pole. The contour lines along which the dip measured at the planet's surface is equal are referred to as isoclinic lines. The points locus which is having a zero dip is known as the magnetic equator or aclinic line.

The dip angle which is also called magnetic dip or magnetic Inclination is the angle made by our planet's magnetic field lines with the horizontal. The angle of dip generally varies from point to point at the surface of the earth and provides information about the movement of the earth’s magnetic field. 

The phenomenon is especially very important in aviation as it causes the compass of the airplane to give erroneous readings during banked turns and airspeed changes. The latter errors generally occur because the card of the compass tilts on its mount when under acceleration.

The needle compasses are often weighed during manufacture to compensate for magnetic dip so we can say that they will balance roughly horizontally. This balancing is usually said to be latitude-dependent.

Angle of dip, commonly known as magnetic dip, is the angle formed by the earth's magnetic field lines intersecting the horizontal.when the horizontal component and the vertical component of the earth's magnetic field are equal. 

The angle of declination between the magnetic field and the horizontal is measured in the vertical plane aligned with magnetic north.

The compass needle is said to point to the magnetic north pole by a lot of people.

This is not geographically true. The compass at that position points in the direction of the horizontal component of the earth's magnetic field. The geomagnetic field and dip graphics below show how the compass needle aligns with the Earth's magnetic field lines.

Magnetic declination is the angle formed by true north (the line leading to the geographical North Pole) and the compass's direction of travel points (the horizontal component of the magnetic field). When using a map and compass, you must account for this declination. There are zones of compass unreliability as you near the magnetic north or south poles, where the compass begins to operate strangely and eventually becomes ineffective.

In addition to secular variations of the magnetic field, magnetic declination or Dip also undergoes more rapid variations due to interactions with the sun. The angle of dip is. Horizontal component of earth's magnetic field becomes zero. The magnetic poles of a freely suspended magnet will become vertical if * = B cos * 


What is Magnetic Dip? 

An inclination of a magnetic needle of a compass with respect to a horizontal surface

Dip is 0 at equator, 90° at poles. 

Dip is not constant. 


Magnetic Declination 

Magnetic declination is the horizontal ∠ between True Meridian & Magnetic Meridian through the pt under consideration. 

Types of Declination 

Declination west (θW)


If the magnetic meridian is on the left side of the true meridian, the angle formed between the two meridians is Declination west. 

Declination east (θE) 

Magnetic meridians are located on the right side of true meridians. The angle formed between these meridians is Declination east.

FAQs on Angle of Dip

1.What is the angle of dip and declination?

The angle of declination is said to be the angle which is between the geographical meridian and the magnetic meridian at a place. It is also known as the magnetic declination at that place. 

The angle of dip is the angle made by the earth's total magnetic field denoted as \[\vec{B}\] with the horizontal direction in the magnetic meridian, known as the angle of dip (δ) at any place.

2.What is the use of the angle of dip?

The angle which is the dip angle or the magnetic dip is the angle that earth's magnetic field makes with the horizontal at any given geographical location. The dip angle is used for measuring as well as correcting the magnetic compass error. It also has its uses in the field of geology and in mapping.

3.Where is the angle of dip 90?

The range of dip angle is from -90 degrees at the North Magnetic Pole to +90 degrees at the South Magnetic Pole. The contour lines along which the dip is measured at the surface of Earth is referred to as isoclinic lines. The locus of the points having a zero dip is known as the magnetic equator or aclinic line.

4.Explain why the angle of declination changes?

This angle generally is said to be depending on the position on the surface of Earth's and changes over time. The angle which is between magnetic and grid meridians is known as the grid magnetic angle or the grid variation. By convention, we can say that the declination is positive when magnetic north is east of true north and negative when it is to the west.

5.Why is the angle of a dip 90 at magnetic poles?

If you think of the earth model that its magnetic field behaves like a deeply buried bar magnet, then at the poles the flux will be directly entering or leaving the  ends of the imaginary magnet, so its direction will be directly in or out of the earth - 90° dip.

The magnetic field is equal in all directions at the magnetic pole's centre. There is no imbalance on it to pull it to any other direction.

6.Explain the difference between a dip angle and a magnetic declination angle?

Angle of Dip :- The angle in the vertical plane to the north magnetic field (magnetic meridian) between the local and horizontal magnetic fields.

Angle of Declination: - Declination is the angle between the magnetic and geographic meridian, or the angle between magnetic north and true north in the horizontal plane.

7.What is the Importance of Magnetic Declination?

Magnetic declination is an important factor to consider while planning your trip. The direction of magnetic power is always indicated by a compass (which join on what are known as the magnetic poles). The declination is the angle created by the geographic North Pole's power direction and bearing. Declination is measured in degrees and minutes east or west to indicate the magnetic field's direction. If a compass at your location indicates true north to the right, then it is positive declination or east, and if it indicates true north to the left, then it is negative declination or west, using degrees and minutes.

8.Is there a place on earth where the dip angle is maximum?  In which direction will a compass needle align itself at the poles? 

Angle of dip is maximum at the poles. Because the N pole of the compass is attracted by the S pole of the earth, the compass needle points north. This does not mean that there is actually a magnet as such inside the earth. If we hold a compass near the North Pole, we will see that the N needle tries to rise straight to the ground due to an electric current in the earth.

9.At the Earth's magnetic poles, what is the angle of dip?

At the poles and the equator, the dip angles are 90 degrees and 0 degrees, respectively. The vertically dipping area is what defines the magnetic poles 

  • A dip or inclination needle is zero at the magnetic equator.

  • A magnetic field surrounds the Earth, which act as a spherical magnet.

  • A dip needle sits upright (dip=90 degrees) at the magnetic poles, the horizontal intensity is zero, and a compass does not reveal direction.

  • The north magnetic pole is marked by the dip needle's north end.

  • The north magnetic pole is up at the south magnetic pole.

  • At the magnetic equator, the dip or inclination is zero.