READ: Electricity

READ: Electricity

A lightning bolt is like the spark that gives you a shock when you touch a metal doorknob. Of course, the lightning bolt is on a much larger scale. But both the lightning bolt and spark are a sudden transfer of electric charge.

Electric charge is a physical property of particles or objects that causes them to attract or repel each other without touching. All electric charge is based on the protons and electrons in atoms. A proton has a positive electric charge, and an electron has a negative electric charge. In the Figure below, you can see that positively charged protons (+) are located in the nucleus of the atom, while negatively charged electrons (-) move around the nucleus.

Electric Force

When it comes to electric charges, opposites attract, so positive and negative particles attract each other. You can see this in the Figure below. This attraction explains why negative electrons keep moving around the positive nucleus of the atom. Like charges, on the other hand, repel each other, so two positive or two negative charges push apart. This is also shown in the diagram. The attraction or repulsion between charged particles is called electric force. The strength of electric force depends on the amount of electric charge on the particles and the distance between them. Larger charges or shorter distances result in greater force. 

Q: How do positive protons stay close together inside the nucleus of the atom if like charges repel each other?

A: Other, stronger forces in the nucleus hold the protons together.

Transferring Electric Charge

Why is this girl's hair standing straight up? She is touching a device called a van de Graaff generator. The dome on top of the device has a negative electric charge. When the girl places her hand on the dome, she becomes negatively charged as well—right down to the tip of each hair! 

Q: What causes the hair to stand on end?

A: All of the hairs have all become negatively charged, and like charges repel each other. Therefore, the hairs are pushing away from each other, causing them to stand on end.

Transferring Electrons

The girl pictured above became negatively charged because electrons flowed from the van de Graaff generator to her. Whenever electrons are transferred between objects, neutral matter becomes charged. This occurs even with individual atoms. Atoms are neutral in electric charge because they have the same number of negative electrons as positive protons. However, if atoms lose or gain electrons, they become charged particles called ions. You can see how this happens in the Figure below. When an atom loses electrons, it becomes a positively charged ion, or cation. When an atom gains electrons, it becomes a negative charged ion, or anion.

Electric Fields

Halt! This science fiction image shows a human hand surrounded by a green force field. It’s supposed to represent an electric field generated by a hand. An electric field is a space around a charged particle where the particle exerts electric force on other charged particles. Because of their force fields, charged particles can exert force on each other without actually touching. Electric fields are generally represented by arrows, as you can see in the Figure below. The arrows show the direction of electric force around a positive particle and a negative particle. 

Interacting Electric Fields

When charged particles are close enough to exert force on each other, their electric fields interact. This is illustrated in the Figure below. The lines of force bend together when particles with different charges attract each other. The lines bend apart when particles with like charges repel each other. 

Q: What would the lines of force look like around two negative particles?

A: They would look like the lines around two positive particles, except the arrows would point toward, rather than away from, the negative particles.

Summary

• Electric charge is a physical property of particles or objects that causes them to attract or repel each other without touching.
• Particles that have opposite charges attract each other. Particles that have like charges repel each other. The force of attraction or repulsion is called electric force.
• Whenever electrons are transferred between objects, neutral matter becomes charged. For example, when atoms lose or gain electrons they become charged particles called ions.
• An electric field is a space surrounding a charged particle where the particle exerts electric force.
• When charged particles are close enough to exert force on each other, their electric fields interact. Particles with opposite charges attract each other. Particles with like charges repel each other.

CC-BY-NC http://www.ck12.org/physical-science/Electric-Charge-and-Electric-Force-in-Physical-Science/lesson/Electric-Charge-and-Electric-Force-MS-PS/?referrer=featured_content
CC-BY-NC http://www.ck12.org/physical-science/Transfer-of-Electric-Charge-in-Physical-Science/lesson/Transfer-of-Electric-Charge-MS-PS/?referrer=featured_content
CC-BY-NC http://www.ck12.org/physical-science/Electric-Fields-in-Physical-Science/lesson/Electric-Fields-MS-PS/?referrer=featured_content