# inductor resistor circuit calculations

Discussion in 'Homework Help' started by lecto1234, May 13, 2015.

1. ### lecto1234 Thread Starter New Member

May 13, 2015
1
0
hi all need some help with this question I already calculated the values for (a), (b) and (d) need help with (c) and (e) thanks.
A circuit comprises an inductor of 9 H of negligible resistance connected in series with a 60Ω resistor and a 240Vd.c. source, Calculate:

(a) The time constant

(b) The current after 1time constant

(c) The time to develop maximum current

(d) The time for the current to reach 2.5A

(e) The initial rate of change of current.

2. ### crutschow Expert

Mar 14, 2008
13,508
3,385
I believe (c) is sort of a trick question.
Think about the equation that describes the current versus time.

Hint: Question (e) involves a first derivative.

3. ### WBahn Moderator

Mar 31, 2012
18,089
4,917
(c) is more of a conceptual question (don't know that I would call it a "trick" question, but can certainly see why some would).

Show your best attempt for (e), starting with the defining equation for the current in an inductor.