﻿ If a doorbell transformer draws 20VA from a 120V source, wha - science mathematics
If a doorbell transformer draws 20VA from a 120V source, wha

## If a doorbell transformer draws 20VA from a 120V source, wha

[From: Engineering] [author: ] [Date: 02-17] [Hit: ]
If a doorbell transformer draws 20VA from a 120V source, what Is the current on the secondary side if it delivers 10V?......

If a doorbell transformer draws 20VA from a 120V source, what Is the current on the secondary side if it delivers 10V?

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Dale-E say: Your specs show a 2 amp current, but truth is, the transformer does not draw 20VA. It is a 20VA transformer, but the draw is half that, or less, typically in most homes. The draw is determined by the bell or chime set attached between the signal button and your 20VA transformer. To know the reality, we need the specs for the bell.
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Mr. Un-couth say: Power required is fixed and pf is fixed.
Let (X) equal magnitude of transformer's secondary current.
Therefore;
(120V)*(.166666667A)*(pf) = (20 VA)*(pf) = (10V)*[(X)A]*(pf)]
20VA = [(10V)*(x)A]
(X) = 2
Transformer's secondary current = 2 Amps
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frank lynn say: 20 VA is the apparent power and as its units implies is Volts x Amperes. So, assuming that the transformer has no losses (not true in the real world but to make this example simple), the input and output power are equal. So 20 VA at a 10Volt load = 20/10 = 2A.
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Philomel say: 20 VA/10V=2A .
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Lee26Caloo秦君子蘭 say: 20/10 = 2A
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billrussell42 say: VA should remain constant, in an ideal world

20 VA = 10 V x current
current = 2 amps

but those transformers are notoriously inefficient, so I'd guess at 1.5 to 1.8 amps
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James say: ?
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