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ANSWERS TO QUESTIONS Q1. THROUGH Q70.

A1. Circuit measurement is used to (1) monitor the operation of a piece of electrical or electronic equipment and (2) determine the reason a piece of electrical or electronic equipment is not functioning properly.
A2. In-circuit meters are used to monitor the operation of electrical or electronic devices.
A3. Out-of-circuit meters can be used on more than one electrical or electronic device.
A4. The compass needle swings away from magnetic north and aligns itself with the magnetic field around the conductor.
A5. If the current increases the magnetic field increases; if the current decreases the magnetic field decreases.
A6. The compass needle will not be deflected as far from magnetic north.
A7. A permanent-magnet moving-coil meter movement used in most electrical and electronic meters.
A8. A magnetic field is generated around the coil and the attraction of this field with the permanent magnet causes the coil to move.
A9. To return the pointer to its rest position when there is no current flow; to oppose the coil movement when there is current flow; to provide electrical connections for the coil.
A10. The compass needle would swing back and forth as the current changed from positive to negative.
A11. The compass needle would vibrate rapidly around the zero-current point ac meter (magnetic north).
A12. A rectifier changes alternating current to pulsating direct current and allows a dc meter to measure ac.
A13. By the use of a rectifier
A14. The process of "smoothing out" the oscillation in a meter movement.
A15. As the coil moves through the field of the permanent magnet, a current is induced in the coil opposing the movement of the coil; and a vane can be attached to the coil and placed in the airtight chamber so that the movement of the vane opposes the movement of the coil.
A16. Average value.
A17. Effective value (rms).
A18. Electrodynamic, moving vane, and hot-wire or thermocouple.
A19. Current.
A20. Current.
A21. In series.
A22. Since the ammeter is a resistor in series with the load, it increases the resistance of the circuit and lowers circuit current.
A23. The resistance of the ammeter must be much smaller than the circuit load.
A24. The amount of current that will cause full-scale deflection.
A25. Shunt resistors (internal or external).
A26. To prevent damage to the meter movement from excessive current.
A27. A range that allows a meter reading near the center of the scale.
A28. Always connect an ammeter in series.
    Always start with the highest range.
    In dc ammeters, observe the proper polarity.
    Deenergize and discharge the circuit before connecting or disconnecting the ammeter.
    Never use a dc ammeter to measure ac current.
    Observe the general safety precautions of electric and electronic devices.
A29. Since the ammeter has a small resistance compared to the load, it will have very high current if it is connected in parallel. This high current will damage the meter.
A30. Voltage.



A31. In parallel.
A32. The connection of a voltmeter adds a resistance in parallel with the circuit changing the total circuit resistance, and loads the circuit.
A33. A voltmeter must have a high resistance compared to the circuit being measured.
A34. Since the resistance of a meter movement remains the same as the pointer is deflected, the amount of current through the movement is proportional to the voltage applied. Therefore, only the scale of the movement must be changed.
A35. It is an indication of the resistance of the meter expressed in ohms per volt. The total resistance of the meter is the sensitivity multiplied by the full-scale voltage.
A36. The use of resistors in series with the meter movement.
A37. To prevent excess current through the meter movement.
A38. Electrostatic.
A39. High-voltage measurement.
A40. Always connect a voltmeter in parallel.
    Always start with the highest range.
    Deenergize and discharge the circuit before connecting or disconnecting the voltmeter.
    In a dc voltmeter, observe the proper polarity.
    Never use a dc voltmeter to measure ac voltage.
    Observe the general safety precautions of electric and electronic devices.
A41. Resistance.
A42. Circuit continuity.
A43. The ohmmeter is connected in series with the resistance to be measured.
A44. An ohmmeter has several internal range resistors and a switch or a series of jacks to select the proper range.
A45. The middle of the scale.
A46. Series and shunt.
A47. Series ohmmeters have 0 on the right end of the scale and ∞ on the left end of the scale. Shunt ohmmeters are the opposite.
A48. Deenergize and discharge the circuit before connecting an ohmmeter.
    Do not apply power to a circuit while measuring resistance.
    Switch ohmmeters to the OFF position, if provided, or to highest range and remove meter leads from the meter when finished measuring resistance.
    Adjust the ohmmeter after changing resistance range and before measuring reading indicates the resistance.
A49. To measure high resistance.
A50. Connect one lead to the insulation and one lead to the conductor. Turn the handcrank until it starts to slip. Note the reading.
A51. Infinity.
A52. Use meggers for high-resistance measurement only.
    Never touch the test leads when the handle is being cranked.
    Deenergize and discharge the circuit completely before connecting a megger.
    Disconnect the item being checked from other circuitry, if possible, before using a megger.
A53. A single measuring device capable of performing the functions of a dc voltmeter and ammeter, an ac voltmeter and ammeter, and an ohmmeter.
A54. It is much more convenient to have one meter with several functions than several meters each with a single function.
A55. By changing the position of the function switch.
A56. The meter movement reacts to average ac voltage and current and the effective value is desired.
A57. To stop parallax error
A58. Make sure no image of the pointer is visible in the mirror when reading the meter.
A59. Deenergize and discharge the circuit completely before connecting or disconnecting a multimeter.
    Never apply power to the circuit while measuring resistance with a multimeter.
    Connect the multimeter in series with the circuit for current measurements, and in parallel for voltage measurements.
    Be certain the multimeter is switched to ac before attempting to measure ac circuits.
    Observe proper dc polarity when measuring dc.
    When you are finished with a multimeter, switch it to the OFF position, if available. If there is no OFF position, switch the multimeter to the highest ac voltage position.
    Always start with the highest voltage or current range.
    Select a final range that allows a reading near the middle of the scale.
    Adjust the "O ohms" reading after changing resistance ranges and before making a resistance measurement.
    Be certain to read ac measurements on the ac scale of a multimeter.
    Observe the general safety precautions for electrical and electronic devices.
A60. To measure current safely and easily (with no need to disconnect the wiring of the circuit).
A61. Power.
A62. Energy.
A63. 5.945 megawatt-hours, or 5,945 kilowatt-hours, or 5,945, 000 watt-hours.
A64. Vibrating reed and moving disk.
A65. A dc ammeter, 90 mA dc
    A dc voltmeter, 200 V dc
    An ac voltmeter, 4.6 V ac
    An ohmmeter, 400 ohms
A66. (A) 410 mA dc; (B) 3.9 mA ac; (C) -22 V dc; (D) 600 V ac; (E) 1.4 V ac; (F) 1.9 kohms (1900&OHgr;).
A67. Figure1-50(D).
A68. (A) Megger (megohmmeter), infinity; (B) Wattmeter, 9.5 kilowatts (9,500 watts). (C) Watt-hour meter, 2.693 megawatt-hours 2,693 kilowatt-hours) (2,693,000 watt-hours).
A69. Yes.
A70. (A) Vibrating-reed, 60Hz. (B) Moving-disk, 58 Hz.




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