Pioneer: In 1785, Charles-Augustin de Coulomb, measured the magnitude of electrostatic forces between charged objects using a torsion balance that he invented.

Nature: Non-contact forces are interactions that can affect a body’s motion without the need to touch it. Non-contact forces can be attractive or repulsive.

Force: A force is attractive if the objects interacting exert a pull on each other, creating a tendency to move closer. On the other hand, a force is repulsive if the interacting objects push each other away.

Types of charges:
1. Positive.
2. Negative.

Same charges: If two objects have the same type of charge the electrostatic force between them will be repulsive. This means that if a positively charged object gets close to another, they both will push each other away. The same occurs for two negatively charged objects.

Opposite charges: On the other hand, opposite charges attract each other. So when one positively charged object is near a negatively charged object, they pull towards each other, tending to move closer.

The earth: The earth is like a giant magnet itself, but its geographic north pole is really a magnetic south pole. Similarly, the geographic South Pole is a magnetic north pole. Because of this, a free-to-move magnet – the needle of a compass, for instance – will always align its magnetic north pole to the earth’s geographical North Pole, and the magnet’s South Pole aligns with the earth’s geographic South Pole. This is why magnets’ poles are named that way.

Magnets: Magnets work due to magnetic forces that occur in atoms forming magnetic zones in the material that act like tiny magnets themselves. Usually, these zones are randomly aligned. However, there is a special type of material called ferromagnetic. They have the property that their magnetic zones align easily when exposed to an external magnetic field, and they maintain this alignment after the magnetic field is gone, becoming magnets themselves! An object that generates a magnetic field due to its internal structure is called a permanent magnet. Ferromagnetic materials are strongly attracted to magnets. Some examples are iron, cobalt, and nickel.

Attraction and Repulsion – Key features:

1. Attraction and repulsion are characteristics of non-contact forces such as electrostatic and magnetic forces.

2. Non-contact forces are interactions that can affect a body’s motion without the need to touch it. Examples of non-contact forces include electric and magnetic forces.

3. Objects having opposite charges experience an attractive electrostatic force, pulling them towards each other.

4. Objects having the same charge experience a repulsive electrostatic force, pushing them away from each other.

5. Like poles of two magnets experience an attractive magnetic force, pulling them towards each other.

6. Opposite poles of two magnets experience a repulsive magnetic force, pushing them away from each other.

7. Coulomb’s law states that the force exerted between two charged objects, whether a force of attraction or repulsion, can be determined by the charge of both objects, the distance between them, and the medium in which the charges are.

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