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# Inductance watch

1. I know this'll seem really obvious to most of you, but I've never studied 'inductance' so have no idea where to even start

'The current in a coil changes from 5A to 2A in 0.05 seconds and induces a voltage of 30V in the coil, the inductance of the coil is?
a) 0.2H
b) 0.5H
c) 1.5H
d) 2.0H

(I don't even know what H is )
Thank-you m'dears!
2. EMF = inductance x rate of change of current

dI/dt = 3/0.05 = 60

so L = 30 / 60 = 0.5H
3. I've almost passed my level 2 c&g tech cert now, but i'm trying to get ahead of the game, if i remember correctly H is (Henry) which is a measure of the inductance of a coil.
I just got this question on a Mock exam and i worked it out like this:

Inductance (L) =
Current change, in this instance (5A-2A) / Rate of change in seconds (0.05s)
so:
3A/0.05s = 60
30v/ 60 = 0.5 Henry

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Updated: June 21, 2012
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