A resistance R and a capacitor C are joined to a source of AC of const

1.	A resistance R and a capacitor C are joined to a source of AC of constant emf and variable frequency. The potential difference across C is V. If the frequency of AC is gradually increased, V will (a) increase (b) decrease (c) remain constant (d) first increase and then decrease
Answer» Correct Answer is: (b) decrease Current i = e/Z = eX/√(R² + X²) where X = 1/ωC. Potential difference across C = V = iX = eX/√(R² + X²) or V = e/√(1 + (R/X)²) = e/√(1 + (ωCR)²). As ω increases, V will decrease

A resistance R and a capacitor C are joined to a source of AC of constant emf and variable frequency. The potential difference across C is V. If the frequency of AC is gradually increased, V will (a) increase (b) decrease (c) remain constant (d) first increase and then decrease

Answer»

Correct Answer is: (b) decrease

Current i = e/Z = eX/√(R² + X²) where X = 1/ωC.

Potential difference across C = V = iX = eX/√(R² + X²)

or V = e/√(1 + (R/X)²) = e/√(1 + (ωCR)²).

As ω increases, V will decrease

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A resistance R and a capacitor C are joined to a source of AC of constant emf and variable frequency. The potential difference across C is V. If the frequency of AC is gradually increased, V will (a) increase (b) decrease (c) remain constant (d) first increase and then decrease

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