Electric Charge and Static Electricity

Transcription

1 Name Date Class Electricity Section Summary Electric Charge and Static Electricity Guide for Reading How do electric charges interact? What is an electric field? How does static electricity build up and transfer? The charged parts of atoms are electrons and protons. Protons and electrons have opposite charges. The charge on the proton is called positive () and the charge on the electron is called negative ( ). Charges that are the same repel each other. Charges that are different attract each other. The interaction between electric charges is called electricity. Force is a push or pull on an object. In electricity, electric force is the attraction or repulsion between electric charges. Electric charges exert force over a distance. An electric field extends around a charged object. An electric field is a region around a charged object where the object s electric force is exerted on other charged objects. When one charged object is placed in the electric field of another charged object, it is either pushed or pulled. It is pushed away if the two objects have the same charge. It is pulled toward the other charged object if their charges are different. You can use electric field lines to represent an electric field. The electric force always points away from positive charges. The strength of an electric field is related to the distance from the charge object. The greater the distance, the weaker the electric field. Electrons can sometimes leave their atoms. An uncharged object becomes charged by gaining or losing electrons. If an object loses electrons, it has an overall positive charge. If an object gains electrons, it has an overall negative charge. The buildup of charges on an object is called static electricity. In static electricity, charges build up on an object, but they do not flow continuously. Charges are neither created nor destroyed. If an object gives up electrons, another object gains those electrons. This is known as the law of conservation of charge. There are three methods by which charges can be transferred to build up static electricity: charging by friction, by conduction, and by induction. Charging by friction is the transfer of electrons from one uncharged object to another by rubbing. Charging by conduction is the transfer of electrons from a charge object to another by direct contact. Charging by induction is movement of electrons to one part of an object that is caused by the electric field of a second object. The electric field around the charged object attracts or repels electrons in the second object. If an object gains a static charge, the object doesn t hold the charge forever. When a negatively charged object and a positively charged object are brought together, electrons transfer until both objects have the same charge. The loss of static electricity as electric charges transfer from one object to another is called static discharge. Lightning is an example of a huge spark of static electricity.

2 Electricity Name Date Class Electric Charge and Static Electricity This section describes how electric charges interact and explains what an electric field is. It also explains what static electricity. Use Target Reading Skills Before you read, preview Figure 4 in your text. Then write two questions that you have about the diagram in the graphics organizer below. As you read, answer your questions. Q. What are the three ways static electricity can be transferred? A. Transferring Static Electricity Q. A. Electric Charge 1. The charge on a proton is called 2. The charge on an electron is called 3. Circle the letter of each statement that is true about interactions between charges. a. Charges that are the same repel each other. b. Charged objects never attract each other. c. Charges that are different attract each other. d. Charged objects always repel each other. 4. Why do protons repel protons but attract electrons? 5. The interaction between electric charges is called

3 Name Date Class Electric Charge and Static Electricity (continued) Electric Force 6. What is electric force? 7. What is a region around a charged object where the object s eletric force is exterted on other charged objects? 8. Electric field lines are drawn with arrows to show the of the electric force. 9. Is the following sentence true or false? The greater the distance, the stronger the electric field. 10. When there are two or more charges, the electric fields of each individual charge by repellng or attracting. Static Electricity 11. Circle the letter of the sentence that explains why there is no overall electric charge in a neutral object. a. In the object s atoms, each positive charge is balanced by a negative charge. b. The object s atoms contain no charged particles. c. The positive charges are attracted to other positive charges. d. In the object s atoms, negative charges outnumber positive charges. 12. How can an object become charged? 13. The buildup of charges on an object is called 14. If an object gains electrons, what will be its overall charge?

4 Electricity Name Date Class Transferring Charge 15. What law states that charges are not created or destroyed? 16. Complete the table about methods of transferring charge. Transferring Charges Method Definition a. The transfer of electrons from one object to another by rubbing b. The transfer of electrons from a charged object to another object by direct contact c. The movement of electrons to one part of an object by the electric field of another object 17. Suppose you dry your clothes in a dryer, and when you take them out they cling to one another. Why do they stick together? 18. An electric charge can be detected by an instrument called a(n) 19. Why do the leaves of an electroscope spread apart when a charged object touches the metal knob?

5 Name Date Class Electric Charge and Static Electricity (continued) Static Discharge 20. What happens when a negatively charged object and a positively charged object are brought together? 21. The loss of static electricity as electric charges transfer from one object to another is called 22. Is the following sentence true or false? Lightning is an example of static discharge.

6 Electricity Name Date Class Electricity Review and Reinforce Electric Charge and Static Electricity Understanding Main Ideas The person whose finger is shown below has walked across a carpet and is about to touch the doorknob. Answer the following questions on a separate sheet of paper. 1. Are the charges in the finger attracted or repelled by the charges in the doorknob? How can you tell? 2. What do the lines around the finger and doorknob represent? 3. One of a kind static electricity is a result of electrons moving into an object from another object. What is another way static electricity can build up in an object? Building Vocabulary From the list below, choose the term that best completes each sentence. conservation of charge static electricity conduction induction static discharge electric field friction electric force 4. In electricity, is the attraction or repulsion between electric charges. 5. The buildup of charges on an object is called 6. The law of states that charges are not created or destroyed. They are transferred. 7. The transfer of charge from one object to another by rubbing is called 8. The loss of static electricity as electric charges transfer from one object to another is called 9. A(n) is a region around a charged object where the object s electric force is exerted on other charged objects. 10. The transfer of electrons from one part of an object to another part, caused by the electric field of another object, without the two objects touching is called 11. The transfer of charge when electrons move from a charged object to another object by direct contact is called