Question

Magnetic moment of the earth is

• A. 8.0 JT\(^{-1}\)
• B. 11.5 JT\(^{-1}\)
• C. \(\pi\)JT\(^{-1}\)
• D. 8.0 x 10\(^{22}\) JT\(^{-1}\)

Hint:

Some physical constants and standard values, like the charge of an electron, Planck's constant, and the magnetic moment of the Earth, are often asked in exams. It's beneficial to memorize the approximate values and their orders of magnitude.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The Earth behaves like a large magnet with a magnetic field extending into space. This magnetic field is generated by the motion of molten iron alloys in its outer core. The strength of this magnetic field is quantified by its magnetic dipole moment. This is a factual, standard value in physics.
Step 2: Detailed Explanation:
The magnetic moment of the Earth has been measured through various geophysical methods. The currently accepted approximate value for the Earth's magnetic dipole moment is about \(8.0 \times 10^{22}\) Joules per Tesla (J T\(^{-1}\)).
The unit J T\(^{-1}\) is equivalent to Ampere-meter squared (A m\(^2\)), which is the standard SI unit for magnetic moment.
Let's check the options:
(A), (B), and (C) present values that are drastically different in magnitude from the known value.
(D) provides the correct order of magnitude and the standard value for the Earth's magnetic moment.
Step 3: Final Answer:
The accepted value for the magnetic moment of the Earth is approximately \(8.0 \times 10^{22}\) J T\(^{-1}\). Therefore, option (D) is correct.