23.6 Back Emf
A spinning motor acting as its own generator, opposing the supply, limiting running current, and explaining large startup surges.
3 exercises
23.6 Exercise 2
Suppose a motor connected to a 120 V source draws 10.0 A when it first starts. (a) What is its resistance? (b) What current does it draw at its normal operating speed when it develops a 100 V back emf?
23.6 Exercise 4
What is the back emf of a 120 V motor that draws 8.00 A at its normal speed and 20.0 A when first starting?
Integrated Concepts
The motor in a toy car is powered by four batteries in series, which produce a total emf of 6.00 V. The motor draws 3.00 A and develops a 4.50 V back emf at normal speed. Each battery has a internal resistance. What is the resistance of the motor?
Adapted from College Physics © 2022 Rice University. Licensed under CC BY 4.0. Sources: College Physics 2e, College Physics for AP® Courses 2e. Imported at revision f98d7a7.