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Calculate current drawn by primary coil of a transformer, Which steps down 200 V to 20 V to operate a device of 20 ohm resistance. Assume efficiency of transformer 80 %.

Text Solution

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Here, `I_(p) = ?, E_(p) = 200 V`,
`E_(s) = 20 V, R_(s) = 20 ohm`
`eta = 80% eta = (E_(s) I_(s))/(E_(p) I_(p)) = (E_(s) (E_(s)//R_(s)))/(E_(p) I_(p))`
`(80)/(10) = (20 xx 20)/(20 xx 200 I_(p)) = (1)/(10 I_(p))`
`I_(p) = (100)/(800) = 0.125 A`
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