Electric Heating MCQs

21. Which of the following does not uses heating effect of electric current?

  1. Electric furnace
  2. Geyser
  3. Electric iron 
  4. Vacuum cleaner

Answer
Answer. d

22. A nichrome wire used as a heater coil has the resistance of 1 ohm meter for a heater of 1000 W at 200V. The length of wire required will be

  1. 5 m
  2. 20 m
  3. 40 m
  4. 50 m

Answer
Answer. c

23. In which type of water heater the heat rays from an element brought up to red heat by the passage of electric current travel through the air rapidly and raise the temperature of the solid substance in the surroundings which falls is its range. 

  1. Three heat switch
  2. Electric iron
  3. Electric oven heating
  4. Electric radiator

Answer
Answer. d

24. Power-factor of industrial arc and induction furnace is

  1. High lagging
  2. High leading
  3. Low lagging
  4. Very low lagging

Answer
Answer. d

25. Two individual heater coils are connected to parallel across the mains. If one of the coil break, the other coil 

  1. Develops lower temperature
  2. Develops same temperature before
  3. Develops higher temperature
  4. Will also not be heated

Answer
Answer. c

26. Furnaces used for cremation use

  1. Resistance heating
  2. Induction heating
  3. Dielectric heating
  4. All of the above

Answer
Answer. a

27. For heating magnetic materials using induction heating, eddy current and hysteresis losses are respectively proportional to

  1. f2 and f
  2. f and f2
  3. f2 and f2
  4. None of the above

Answer
Answer. a

28. The normal voltage used for dielectric heating is

  1. 1500 V
  2. 15 kV
  3. 30 kV
  4. 33 kV

Answer
Answer. a

29. When a hot-plate is connected to the mains, its element becomes red hot, but the copper wire in the leads remain cool. This is due to

  1. The element is coiled, but the copper wire is not
  2. Length of the element is more than the copper wire
  3. Copper wire is thinner than the element
  4. The element has a high resistance than the copper wire

Answer
Answer. d

30. A body at temperature T K radiates heat in proportion to

  1. T2
  2. 1/T2
  3. T4
  4. 1/T4

Answer
Answer. c

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