06-04-2021, 11:42 AM
(This post was last modified: 06-04-2021, 12:01 PM by peter scott.)
I've been trying to get my head round some of the numbers. According to Sir J.A. Fleming in his book "The Principles of Electric Wave Telegraphy and Telephony" the capacitor at Clifden was 1.16uF and was charged up to 80kV. (Page 255.)
Both these numbers are puzzling. We know that in the "Condenser House" there were 1800 plates 30' high by 12' wide with 12" spacing. The shed was 360' long by 75' wide. Well that would certainly fill most of the shed allowing some space for the actual spark transmitter. An air spaced multiplate capacitor with those dimensions would have a capacitance of 1.76uF which doesn't fit with the Fleming figure but we need to partition this total between the three capacitors in the diagram and we also need to account for the 80kV voltage from the 12kV generator. I think that the capacitors K each charge up to 6kV on sparking but transfer their charges to E in opposite senses so each of K imparts 40kV on E so the ratio of each K to E must be 6.66. With a total size of 1.76uF E must be 0.123uF and the two Ks 0.818uF each.
So where does Fleming's 1.16uF fit in? Someone got something wrong somewhere and I don't imagine it was Fleming.
Peter
Both these numbers are puzzling. We know that in the "Condenser House" there were 1800 plates 30' high by 12' wide with 12" spacing. The shed was 360' long by 75' wide. Well that would certainly fill most of the shed allowing some space for the actual spark transmitter. An air spaced multiplate capacitor with those dimensions would have a capacitance of 1.76uF which doesn't fit with the Fleming figure but we need to partition this total between the three capacitors in the diagram and we also need to account for the 80kV voltage from the 12kV generator. I think that the capacitors K each charge up to 6kV on sparking but transfer their charges to E in opposite senses so each of K imparts 40kV on E so the ratio of each K to E must be 6.66. With a total size of 1.76uF E must be 0.123uF and the two Ks 0.818uF each.
So where does Fleming's 1.16uF fit in? Someone got something wrong somewhere and I don't imagine it was Fleming.
Peter
