**Historical Background from NDT ( Nondestructive Testing) Resource Center**

1. a. The first recorded references to static electricity and lightning were made over 2,500 years ago by _______.

** **b. Describe the first experiment with static electricity

2. In 1600, Dr. William Gilbert coined the term “*electrica,*” a word that gave rise to our word electricity. What does this term “*electrica”* describe?

**Basics of Electricity – Amperage**

8. What unit measures the flow of electrons?

9. How is an amp defined?

10. What is a coulomb?

11. Name the instrument used to measure the amount of amps flowing in an electrical circuit.

12. What is the force that causes electrons to move in an electrical circuit?

13. Name 3 sources of EMF.

14. What happens to the electron flow within a conductor if the EMF or voltage source is removed?

15. What unit used to measure EMF?

16. What is a volt?

17. What is resistance?

18. In what units is resistance measured?

19. Define the term: ohm.

20. State one example when resistance is desirable.

21. State one example when resistance is undesirable.

22. What components are placed in an electrical circuit to control the amount of resistance in circuit?

**George Simon Ohm (1789 to 1854) was a mathematics teacher who became interested in the new field of electricity.**

23. In 1827, George Ohm developed a mathematical relationship between voltage, current, and resistance called ____.

24. a. State Ohm’s Law in a mathematical equation.

b. What do the following variables represent? Use the symbols below to fill in the triangle at right.

I = ____________________________

V = ____________________________

R = ____________________________

25. Using the equation, I = V / R, describe the following:

a. If the voltage is increased what will happen to the current?

b. If the resistance is increased what will happen to the current?

26. Using the second equation, V = I • R, describe the following:

a. If either the current or the resistance is increased in the circuit, what will happen to the voltage?

27. Using the third equation, R = V / I, describe the following:

a. If the voltage is increased what will happen to the resistance?

b. If the current is increased what will happen to the resistance?

28. What is the symbol of an ohm?

29. How is a circuit formed?

30. Explain the relationship of potential and kinetic energy to electricity.

40. Build the series circuit at this web site.

41. Describe a series circuit.

42. What is a load in a circuit?

43. What is a short circuit?

44. What is used in an electrical circuit to prevent a short circuit?

45. Build the series circuit with resistors at this web site.

46. Build the parallel circuit at this web site.

47. Describe a parallel circuit.

48. Build the parallel circuit with a voltmeter at this web site.

49. How is the ammeter always placed in a circuit?

50. How is the voltmeter always placed in a circuit?

51. Build the series / parallel circuit at this web site.

52. List the components that are connected in series from the circuit you just constructed.

53. List the components that are in parallel from the circuit you just constructed.

54. What does DC mean in terms of electrical current?

55. What do we use every day in our electronic devices that is a good source of direct current?

56. What does AC mean in terms of electrical current?

57. How often is the current alternating directions?