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Ohms addition / subtraction
Posted: Sat Oct 06, 2012 9:32 pm
Author: Al
Does a pair or 1.5 ohm (Brown / Red) Dyna coils sum to 3 ohms when wired in series?
Or is resistance not an addition process but an iterative one?
This is for a four coil setup on a bike with an 8 plug head running Dyna 'S'.
I believe the correct resistance should be 3 ohms for Dyna 'S' but with four coils (1.5 ohms each) i need to check the value of 2 times 1.5 in series.
Reason for asking is i have seen it done with four Grey Dyna coils of value 2.2 ohms.
AL
Posted: Sun Oct 07, 2012 4:44 am
Author: london calling
Resistance in series is added together,eg 2=2+4
In parallel it's the reciprocal of the reistances combined,then reciprocated

again.
This means the overall resistance is always less than the smallest resistance.
Posted: Sun Oct 07, 2012 6:53 am
Author: KeithZ1R
connect em up and measure it

although from my dim and distant classroom days coils are measured in inductance so it may not be that simple although as Jack has pointed out series is summing parallel is reciprocal summing
Posted: Sun Oct 07, 2012 7:08 am
Author: ZedHead
london calling wrote:Resistance in series is added together,eg 2=2+4
In parallel it's the reciprocal of the reistances combined,then reciprocated

again.
This means the overall resistance is always less than the smallest resistance.
Correct
Resisters in series R = R1 + R2 +R3 etc
Resisters in parallel = 1/R = 1/R1 + 1/R2 + 1/R3 etc
Posted: Sun Oct 07, 2012 8:06 am
Author: garyd
Resisters in parallel = 1/R = 1/R1 + 1/R2 + 1/R3 etc[/quote]
A different way to write it if you understand maths
Resisters in parallel = R = 1 / ((1/R1) + (1/R2) + (1/R3))
Posted: Sun Oct 07, 2012 8:33 am
Author: Al
Outstanding gents, thank you all.
AL
Posted: Sun Oct 07, 2012 3:14 pm
Author: Taffus
KeithZ1R wrote:connect em up and measure it

although from my dim and distant classroom days coils are measured in inductance so it may not be that simple although as Jack has pointed out series is summing parallel is reciprocal summing
You're thinking of dynamic impedance
Z
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Posted: Sun Oct 07, 2012 7:04 pm
Author: KeithZ1R
thats the one

what a bastard equation that was

Posted: Sun Oct 07, 2012 7:39 pm
Author: Taffus
1 over 2 pi root lc that is the resonant frequency.......
is that my anorak?

Posted: Sun Oct 07, 2012 7:49 pm
Author: Z1parR
For gods sake you sparks , glad i'm a mechanical fitter
What was it again about the East coast line engine that pulled the 8 carriage and buffet car

Posted: Sun Oct 07, 2012 7:49 pm
Author: KeithZ1R
nope just a better memory

now without google the transformer efficiency equation please

Posted: Sun Oct 07, 2012 8:18 pm
Author: Taffus
KeithZ1R wrote:nope just a better memory

now without google the transformer efficiency equation please

or the square root of -1
