A constant current of I = 15 A exists in a solenoid whose inductance is L = 2.8 H. The current is then reduced to zero in a certain amount of time. (a) If the current goes from 15 to 0 A in a time of 75 ms, what is the emf induced in the solenoid? (b) How much electrical energy is stored in the solenoid? (c) At what rate must the electrical energy be removed from the solenoid when the current is reduced to 0 A in a time of 75 ms? Note that the rate at which energy is removed is the power.

Question

Moshe Tucker

Physics

6 April, 21:31

A constant current of I = 15 A exists in a solenoid whose inductance is L = 2.8 H. The current is then reduced to zero in a certain amount of time. (a) If the current goes from 15 to 0 A in a time of 75 ms, what is the emf induced in the solenoid? (b) How much electrical energy is stored in the solenoid? (c) At what rate must the electrical energy be removed from the solenoid when the current is reduced to 0 A in a time of 75 ms? Note that the rate at which energy is removed is the power.

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Answers (1)

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Charlize Hubbard · Answer 1

Given that

Constant current I=15A

Inductance L=2.8H

a. Current changes from 15A to 0A.

∆I=0-15=-15

For a time of t=75ms=0.075s

EMF=?

EMF is given at

EMF=-L (∆I/t)

EMF=-2.8*-15/0.075

EMF=3.15V

b. Energy stored?

Energy stored is given as

E=½LI²

E=½*2.8*15²

E=315 J

c. Rate of energy? Which is power and the rate of energy is given as

Power=Energy/timetaken

Power=315/0.075

Power=4200W

P=4.2KW