12th Class Physics Electrostatics & Capacitance Question Bank

done Case Based (MCQs) - Electrostatic Potential and Capacitance Total Questions - 15

• question_answer1)

  Directions (Q. No. 1 to 5):

  Read the following text and answer the following questions on the basis of the same:

  Super capacitor: Super capacitor is a high capacity capacitor with a capacitance value much higher than normal capacitors but with lower voltage limits. Such capacitors bridges the gap between electrolytic capacitors and rechargeable batteries.

  In automobile, bus, train, crane, elevator such capacitors are used for regenerative braking, short term energy storage or burst-mode power delivery.

  Super capacitors have many advantages over batteries: they are very low weight and generally don't contain harmful chemicals or toxic metal.

  They can be charged and discharged innumerable number of times without ever wearing out.

  The disadvantage is that super capacitors aren't well-suited for long-term energy storage. The discharge rate of super capacitors is significantly higher than lithium-ion batteries; they can lose as much as 10-20% of their charge per day due to self- discharge.

  Capacity of super capacitor is:
  A)
  very low. done clear
  B)
  medium. done clear
  C)
  very high. done clear
  D)
  may have any value. done clear
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• question_answer2)
  Super capacitor makes a bridge between:
  A)
  electrolytic capacitor and rechargeable battery. done clear
  B)
  single use battery and electrolytic capacitor. done clear
  C)
  electrolytic capacitor and dynamo. done clear
  D)
  electrolytic and non-electrolytic capacitors. done clear
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• question_answer3)
  Super capacitors can be charged and discharged:
  A)
  few number of times. done clear
  B)
  once only. done clear
  C)
  several number of times but less than rechargeable batteries. done clear
  D)
  several number of times much more than rechargeable batteries. done clear
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• question_answer4)
  Self-discharge rate of Super capacitors:
  A)
  10-20% of their charge per day done clear
  B)
  1 - 2% of their charge per day done clear
  C)
  0% of their charge per day done clear
  D)
  100% of their charge per day done clear
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• question_answer5)
  Super capacitors are used for
  A)
  degenerative braking. done clear
  B)
  regenerative braking. done clear
  C)
  small appliances. done clear
  D)
  long time charge storage. done clear
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• question_answer6)

  Directions (Q. No. 6 to 10):

  Read the following text and answer the following questions on the basis of the same:

  Capacitor Colour Code:

  Capacitor values as written on small capacitors are sometimes misleading. Letters like p (pico) or n (nano) are used in place of the decimal point to identify its position and the value of the capacitor.

  For   example,   a   capacitor   labelled   as n33 = 0.33nF, 8n2 = 8.2nF, 22n = 47nF and so on.

  Sometimes capacitors are marked with the capital letter K to signify a value of Kilo pico-Farads.

  As for example, a capacitor with the markings of 100K would be \[1000\times 100pF=100Kpf=100\text{ }nF\].

  Sometimes, a three letter code consists of the two value digits and a multiplier. For example, the digits \[471=47\times 10=470pF,332=33\times 100=3300p\].

  To reduce these confusions an International colour coding scheme was developed almost same as that of resistance colour code. Band Digit  1 Digit  2 Multiplier Colour       Black 0 0 \[\times \]1 Brown 1 1 \[\times \]10 Red 2 2 \[\times \]100 Orange 3 3 \[\times \]1000 Yellow 4 4 \[\times \]10,000 Green 5 5 \[\times \]1,00,000 Blue 6 6 \[\times \]10,00,000 Violet 7 7   Grey 8 8 \[\times \]0.01 White 9 9 \[\times \]0.1

  The value obtained from colour code is in pf.

  What is the value of the capacitor if n27 is written on it?
  A)
  0.27 nF done clear
  B)
  0.27 pF done clear
  C)
  27 nF done clear
  D)
  27 pF done clear
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• question_answer7)
  Two capacitors marked as 221 and 220 respectively are joined in parallel. What is the total capacitance value?
  A)
  441 pF done clear
  B)
  242 pF done clear
  C)
  242 nF done clear
  D)
  441nF done clear
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• question_answer8)
  68k is written on a capacitor. What is its value?
  A)
  68 pF done clear
  B)
  68 nF done clear
  C)
  68 µF done clear
  D)
  None of these. done clear
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• question_answer9)
  What is the value of the capacitor bearing a colour code: brown, green, brown?
  A)
  15 pF done clear
  B)
  15 nF done clear
  C)
  15 nF done clear
  D)
  150pF done clear
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• question_answer10)
  What will be the colour code of a 27 nF capacitor?
  A)
  Red, violet, black done clear
  B)
  Red, violet, brown done clear
  C)
  Red, violet, orange done clear
  D)
  None of the above done clear
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• question_answer11)

  Directions (Q. No. 11 to 15):

  Read the following text and answer the following questions on the basis of the same:

  Power factor corrector capacitor

  Power factor correction is a method to reduce the lagging power factor in inductive loads by fixing a high value capacitor across the phase and neutral line close to the load. When the Voltage and Current are in phase with each other in an AC circuit, the energy from the source is fully converted into another form to drive the load and in this case power factor is in unity. When the power factor drops, the system becomes less efficient.

  In inductive loads, current "lags" the voltage leading to "lagging power factor". Power factor correction is the method to reduce the lagging                                                                                                                                                                                                                                                                                                                          power factor in inductive loads by fixing a high value capacitor across the phase and neutral close to the load. These capacitors have leading power factor so that it will neutralize the lagging power factor of the load.

  Power capacitors are huge non polarized metal film electrolytic type capacitors.

  Capacitors should be sufficiently rated to the load capacity. It should be connected to the lines, only when the loads are running and drawing current

  What is meant by power factor correction?
  A)
  The method to reduce the lagging power factor in inductive loads done clear
  B)
  The method to enhance the lagging power factor in inductive load done clear
  C)
  The method to reduce the lagging power factor in capacitive loads done clear
  D)
  The method to enhance the lagging power factor in capacitive loads done clear
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• question_answer12)
  When the energy from source is fully converted into another form, the power factor is
  A)
  0.5 done clear
  B)
  1.0 done clear
  C)
  0 done clear
  D)
  \[\infty \] done clear
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• question_answer13)
  Power capacitors for power factor correction are
  A)
  polarized metal film electrolytic type. done clear
  B)
  non-polarized metal film electrolytic type. done clear
  C)
  non-polarized metal film non-electrolytic type. done clear
  D)
  polarized ceramic non-electrolytic type. done clear
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• question_answer14)
  Power capacitors for power factor correction have
  A)
  lagging power factor. done clear
  B)
  leading power factor. done clear
  C)
  leading or lagging power factor depending on the value of the capacitor. done clear
  D)
  leading or lagging power factor depending on the type of load. done clear
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• question_answer15)
  Power factor corrector capacitors should be connected
  A)
  across the phase and ground near the inductive load. done clear
  B)
  across the phase and neutral away from the inductive load. done clear
  C)
  across the phase and neutral near the inductive load. done clear
  D)
  across the neutral and ground near the inductive load. done clear
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