GRE Reading Comprehension

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Source: 1999

Benjamin Franklin established that lightning is the transfer of positive or negative electrical charge between regions of a cloud or from cloud to earth. Such transfers require that electrically neutral clouds, with uniform charge distributions, become electrified by separation of charges into distinct regions. The greater this separation is, the greater the voltage, or electrical potential of the cloud. Scientists still do not now the precise distribution of charges in thunderclouds nor how separation adequate to support the huge voltages typical of lightning bolts arises. According to one theory, the precipitation hypothesis, charge separation occurs as a result of precipitation. Larger droplets in a thundercloud precipitate downward past smaller suspended droplets. Collisions among droplets transfer negative charge to precipitating droplets, leaving the suspended droplets with a positive charge, thus producing a positive dipole in which the lower region of the thundercloud is filled with negatively charged raindrops and the upper with positively charged suspended droplets.

Question List: 1 2 3 4

The passage suggests that lightning bolts typically

  • A produce a distribution of charges called a positive dipole in the clouds where they originate
  • B result in the movement of negative charges to the centers of the clouds where they originate
  • C result in the suspension of large, positively charged raindrops at the tops of the clouds where they originate
  • D originate in clouds that have large numbers of negatively charged droplets in their upper regions
  • E originate in clouds in which the positive and negative charges are not uniformly distributed

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