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ANSWERS TO QUESTIONS Q1. THROUGH Q43.

A1. An electrical current which flows in one direction only.
A2. An electrical current which is constantly varying in amplitude, and which changes direction at regular intervals.
A3. The dc voltage must be generated at the level required by the load.
A4. The I²R power loss is excessive.
A5. Alternating current (ac).
A6. The needle aligns itself at right angles to the conductor.
A7. (a) clockwise (b) counterclockwise.
A8. It is used to determine the relation between the direction of the magnetic lines of force around a conductor and the direction of current through the conductor.
A9. The north pole of the compass will point in the direction of the magnetic lines of force.
A10. It combines with the other field.
A11. It deforms the other field.
A12. (a) The field consists of concentric circles in a plane perpendicular to the wire (b) the field of each turn of wire links with the fields of adjacent turns producing a two-pole field similar in shape to that of a simple bar magnet.
A13. The polarity of the two-pole field reverses.
A14. Use the left-hand rule for coils.
A15. Grasp the coil in your left hand, with your fingers "wrapped around" in the direction of electron flow. The thumb will point toward the north pole.
A16. (a) When the conductors are cutting directly across the magnetic lines of force (at the 90° and 270° points). (b) When the conductors are moving parallel to the magnetic lines of force (at the 0°, 180°, and 360° points).
A17. 360°.
A18. Extend your left hand so that your thumb points in the direction of conductor movement, and your forefinger points in the direction of the magnetic flux (north to south). Now point your middle finger 90° from the forefinger and it will point in the direction of electron current flow in the conductor.
A19. Continuous rotation of the conductor through magnetic fines of force produces a series of cycles of alternating voltage or, in other words, an alternating voltage or a sine wave of voltage.
A20. Frequency is the number of complete cycles of alternating voltage or current completed each second.
A21. Period.
A22. A positive alternation is the positive variation in the voltage or current of a sine curve.
A23. The period measures time and the wavelength measures distance.
A24. The peak value is the maximum value of one alternation; the peak-to-peak value is twice the maximum or peak value.
A25. Twice.

A26. The instantaneous value (E_inst or I_inst )
A27. Average value (E_avg or I_avg)
A28. Zero
A29.
A30.
A31.
A32. The power (heat) produced in a resistance by a dc voltage is compared to that produced in the same resistance by an ac voltage of the same peak amplitude.
A33. The effective value.
A34.
A35.
A36. (Remember: Unless specified otherwise, the voltage or current value is always considered to be the effective value.)
A37. When the two waves go through their maximum and minimum points at the same time and in the same direction.
A38. When the waves do not go through their maximum and minimum points at the same time, a PHASE DIFFERENCE exists, and the two waves are said to be out of phase. (Two waves are also considered to be out of phase if they differ in phase by 180° and their instantaneous voltages are always of opposite polarity, even though both waves go through their maximum and minimum points at the same time).
A39. They are in phase with each other.
A40. Locate the points on the time axis where the two waves cross traveling in the same direction. The number of degrees between these two points is the phase difference.
A41.
A42. I_avg = 0.636 X I_max = 1.41 amperes.
A43. 43.3 ohms.