Counter emf generated in a motor at full speed

  • Thread starter lloyd21
  • Start date
  • #1
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Homework Statement


An electric motor draws 20.0 A of current when first switched on. The motors windings have a resistance of 5.0 ohm. Once the motor is up to full speed it draws only 4.4 A of current. Calculate the counter emf generated in the motor at full speed

Homework Equations


I = V/R
V=IR

The Attempt at a Solution


R = 5.0 ohm
A1 = 20.0 A
A2= 4.4 A n

1. (20A)(5.0ohm) = 100 V

2. (4.4A)(5.0ohm) = 22V

3. 100V - 22V = 78V

Im told im missing some "change", however I think this is correct, it is change in voltage?
 

Answers and Replies

  • #2
andrevdh
Homework Helper
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116
Looks fine to me.
 

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