(a) Find the current in the coils when the motor is first turned on. A (b) Find

Question

(a) Find the current in the coils when the motor is first turned on.
A

(b) Find the current in the coils when the motor has reached maximum speed.
A

(c) If the current in the motor were 6.0 A at some instant, what is the back emf at that time?
V

A motor has coils with a resistance of 25 ohm and operates from a voltage of 237 V. When the motor is operating at its maximum speed, the back emf is 149 V. (a) Find the current in the coils when the motor is first turned on. A (b) Find the current in the coils when the motor has reached maximum speed. A (c) If the current in the motor were 6.0 A at some instant, what is the back emf at that time? V

Explanation / Answer

a) Just as the current is turned on ,

the coils resist the flow of current ,

and hence , the net current is ZERO

B)

Using Ohm's law

V = IR

237 - 149 = I*25

I = 3.52 A

the current in the coils is 3.52 A

C)

Here , Using Ohm's law

V = IR

237 - E = 6*25

E = 87 V

the back EMF at this instant is 87 V

Related Questions

Navigate

• Browse (All)
• Browse #
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.