F. H. Richardson's bluebook of projection (1935)

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GROUNDS 1. What two types of grounds are there? 2. Why are permanent grounds employed ? 3. Is current leakage set up by grounding one wire of a circuit ? 4. Do earth grounds offer variable resistance? 5. May a positive and negative have earth ground with but little current flow? 6. May a ground through something other than earth offer sufficient resistance to prevent current leakage? 7. If one polarity grounds to the lamp frame and the other does not, what is the effect? 8. How may slight current leakage sometimes be set up ? 9. With what may grounds be tested? \ 10. If the test lamp, bell and battery or magneto is connected across a ground, will the lamp light or the bell ring? 11. Is failure of lamp to light or bell to ring conclusive proof that there is no ground? 12. Why must all high resistance grounds be detected? 13. Why will a test lamp not light when connected across an Edison 3-wire neutral ground? 14. What is the surest way of testing an Edison 3-wire circuit in which the neutral is involved? 15. Should projection rooms be equipped with a magneto? ■ 16. Describe a 110-220 volt test lamp. 17. How many batteries (dry cells) should be used for testing. and how should they be connected? 18. Why is one dry cell insufficient for ground testing? ' 49. How would you proceed to test your arc lamp for ground" 20. How would you proceed to install a permanent test lamp? 21. What wire would you use if a ground to earth is suspected. 22. When testing for ground in your lamp, should permanenl ground of both test lamp and projector be disconnected : 23. What various equipments should be grounded and why! 24. How often should equipments be tested for ground? 51