Question

Which of the following physical properties of the Earth's mantle controls the transmission of geomagnetic signals from the core to the surface?

• A. electrical conductivity
• B. electrical voltage
• C. electric rotational energy
• D. electric current

Hint:

Magnetic signals travel through the mantle depending on its electrical conductivity.

Answer 1

The Correct Option is A

To determine which physical property of the Earth's mantle facilitates the transmission of geomagnetic signals from the core to the surface, we need to examine the electromagnetic processes involved.

1. Geomagnetic Field Generation:
The Earth's magnetic field originates from the geodynamo process in the outer core, where convective motion of molten iron alloys generates electric currents, which in turn produce magnetic fields.

2. Signal Transmission Mechanism:
For these magnetic signals to reach the surface, they must pass through the mantle. The key property enabling this transmission is:

• Electrical conductivity: The ability of mantle materials to permit the flow of electric currents induced by the core's changing magnetic field

3. Why Other Options Are Incorrect:
- Electrical voltage: A potential difference, not a material property
- Electric rotational energy: Not a standard physical property of materials
- Electric current: A flow of charge, not an intrinsic material property

4. Scientific Evidence:
Studies of:

• Electromagnetic induction in the mantle
• Laboratory measurements of mantle mineral conductivity
• Observations of geomagnetic secular variation

all confirm electrical conductivity as the controlling factor.

Final Answer:
The property controlling geomagnetic signal transmission is $\boxed{\text{electrical conductivity}}$.