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Question
A 60 W load is connected to the secondary of a transformer whose primary draws line voltage. If a current of 0.54 A flows in the load, what is the current in the primary coil? Comment on the type of transformer being used.
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Solution
PS = 60 W, IS = 0.54 A, IP = ?
PS = VSIS
60 = VS × 0.54
`60/0.54` = VS
VS = 111.10 Volt
In multiple of 11
VS = 110 Volt
Ratio factor of transformer 'r` = output voltage/input voltage
`r = V_S/V_P` ⇒ `r = (110 "Volt")/(220 "Volt") = 1/2`
Or r < 1, so transformer is step down transformer.
In transformer, output power = input power.
ISVS = IPVP
`I_P = (I_SV_S)/V_P = (0.54 xx 110)/220`
IP = 0.27 ampere
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