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Question
An alternating voltage of 220 V is applied across a device X. A current of 0.22 A flows in the circuit and it lags behind the applied voltage in phase by π/2 radian. When the same voltage is applied across another device Y, the current in the circuit remains the same and it is in phase with the applied voltage.
- Name the devices X and Y and,
- Calculate the current flowing in the circuit when the same voltage is applied across the series combination of X and Y.
Solution
- X is a resistor and Y is the capacitor.
R = `V_{rms}/I_{rms} = 220/0.22 = 1000 Omega`
R = XC = 1000Ω
When R and C are in series.
`I_{rms} = V_{rms}/Z = V_{rms}/sqrt(R^2 + (X_C)^2)`
= `220/sqrt((1000)^2 + (1000)^2)`
= `220/(1000 xx sqrt2)`
`I_{rms} = 0.156` A
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