In a DC generator, brushes are made of _______.

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SSC JE EE Previous Paper 11 (Held on: 24 March 2021 Morning)
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  1. copper
  2. aluminium
  3. carbon or graphite
  4. laminated steel

Answer (Detailed Solution Below)

Option 3 : carbon or graphite
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Brushes in DC machine:

  • Brushes are used to collect the current due to the induced emf from the armature coils in a DC generator
  • Brushes are made up of Carbon and graphite to reduce the wear and tear of the commutator
  • When a brush is at any particular segment, it shorts out that particular coil and draws current from the rest of the coils
  • If emf induce in that coil, the huge current will flow
  • To prevent this, brushes are positioned in such a way that the coil being short-circuited has no emf in it to prevent heat loss in the brushes and sparking at commutator segments
  • Hence brushes placed along the magnetic neutral axis
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