Photocells are used

A. in burglar alarms

B. in automotive devices for light switches

C. television cameras

D. All the above

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  1. One finds it more difficult to walk on ice than on a concrete road because
  2. In an electrical circuit, a fuse is connected
  3. The force of attraction or repulsion between two charged bodies is directly proportional to the product…
  4. Out of the following which is an insulator?
  5. In a freezer ice cubes will be formed more quickly in trays made of
  6. For accurate scientific work, temperatures are often measured by
  7. A rod of brass la held in hand and rubbed with fur. The rod is found to have
  8. Which of the following is known as freon?
  9. A bolometer is used to measure
  10. When a light ray is reflected repeatedly by a set of parallel plane mirrors, the intensity of light…
  11. A light year means
  12. The velocity of sound in a medium is
  13. When an electric bulb breaks, there la an explosive sound. That is due to
  14. The Space Application Centre for training in Satellite Communication Technology is located at
  15. X-rays were discovered by
  16. It is difficult to bon potatoes at the top or a mountain because
  17. In hot climatic conditions, the buildings are painted white because
  18. The mixing up of two gases as a result of random motion of molecules is called
  19. The loudness of a sound is determined by
  20. A star contains
  21. The spectrum of white light can be studied by
  22. Like magnetic poles
  23. In the electrical circuit of a house the fuse acts as
  24. Which of the following is fissionable?
  25. Resistance is measured in
  26. Two tumblers stuck together can be separated by
  27. In the fuse of an electrical installation blows out
  28. An integrated circuit la more advantageous than a conventional circuit because
  29. The radius of an atom is approximately
  30. Water has maximum density at