Question

1. what causes earth to act like a bar magnet? *

a. its core is made of nickel
b. its core is made of iron
c. the rotation of earth
d. the revolution of earth around the sun
10 points

Explanation:

The Earth acts like a bar magnet mainly due to the movement of molten iron in its outer core (the dynamo effect). However, options a (core is nickel - while nickel is present, iron is more crucial for magnetism), b (core is iron - correct material but not the full reason), c (rotation - part of the dynamo effect mechanism), d (revolution - not related to magnetism). The key is the combination of the core's iron content and the Earth's rotation (the rotation is part of what drives the dynamo effect). But among the given options, the rotation of Earth (option c) is a key factor as it, along with the conductive iron - rich core, creates the magnetic field (through the dynamo effect).

Answer:

c. the rotation of Earth