going through a practice question paper and theres a few questions I am struggling to find awnswers for in my notes, not sure which formula I need here but one of the questions is;

A self induced e.m.f. of 60 Volts is produced by a current of 6 amperes in 0.4 seconds. What is the inductance of the inductor?

a 15H coil (inductor) carries a current of 7A. What amount of energy is stored in the magnetic field?

Need to know the Frequency applied to this Inductor, to figure Xl. (BTW: "pi" = Greek lower case "pi", or 3.141592653589...)

Formula is: XL = 2pi FL

If F= 60Hz, then XL =:

2 * 3.141592653589 * 60 * 15.0 = 5,654 Ohms

Find Voltage: E=IR I = 7.0 Amps, R = 5,654 Ohms 7.0 * 5,654 = 39,578 Volts.

Find Reactive Power: VAR= E * I

E = 39,578 Volts, I = 7.0 Amps VARs = 277,046 VARs.

--- Personal Note:

I think the value of the Inductor is quite large - 15H.

Substituting 0.0015H (15mH) for the Inductor results in a much more reasonable Reactive Component: 277.046 VARs, with a Potential Difference of 39.578 Volts (rounded to 40 Volts).

-- Scott (EE)

---let's see if these spec. characters work now!---

Last edited by Scott35; 05/20/1203:26 PM. Reason: Nope, symbols will not work!

Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!

Re: Which bright spark can help me here?
[Re: Scott35]
#206096 05/20/1201:03 PM05/20/1201:03 PM