Page 1 - Worksheet 2

Worksheet_2

Alternating current

1 In an LCR-series ac circuit, the voltage across each of the component L, C and R is 50 V. The
voltage across the LC-combination will be
(a) 50 V
(b) 50√2 V
(c) 100 V
(d) zero
2 In an LCR circuit, capacitance is charged from C to 2C. For resonant frequency to remain
unchanged, the inductance should be changed from L to
(a) 4 L
(b) 2 L
(c) L/2
(d) L/4
3 If coil is open, then L and R becomes
(a) infinity, zero
(b) zero, infinity
(c) infinity, infinity.
(d) zero, zero
4 What is the value of inductance L for which the current is maximum in a series LCR- circuit
with C = 10 μF and ω = 1000 s-1?
(a) 100 mH
(b) 1 mH
(c) 10 mH
(d) cannot be calculated unless R is known
5 An AC voltage source of variable angular frequency ω and fixed amplitude V connected in
series with a capacitance C and an electric bulb of resistance R (inductance zero). When ω is
increased
(a) The bulb glows dimmer
(b) The bulb glows brighter
(c) Net impedance of circuit is unchanged
(d) Total impedance of the circuit increases