Why is choke coil needed in the use of fluorescent tubes with ac mains?

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Solution

In a.c. circuits, a choke coil is used to control the current in place of a resistance. If a resistance is used to control the current, the electrical energy will be wasted in the form of heat. Due to its inductive reactance, a choke coil decreases the current without wasting electrical energy in the form of heat.

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Q. Why choke coil is needed in the use of flourescent tube with ac mains why cannot we use ordinary resistor instead of it

Why choke coil is used in fluorescent tubes

Q. Answer the following questions::

(a) In any ac circuit, is the applied instantaneous voltage equal to the algebraic sum of the instantaneous voltages across the series elements of the circuit? Is the same true for rms voltage?

(b) A capacitor is used in the primary circuit of an induction coil.

(c) An applied voltage signal consists of a superposition of a dc voltage and an ac voltage of high frequency. The circuit consists of an inductor and a capacitor in series. Show that the dc signal will appear across C and the ac signal across L.

(d) A choke coil in series with a lamp is connected to a dc line. The lamp is seen to shine brightly. Insertion of an iron core in the choke causes no change in the lamps brightness. Predict the corresponding observations if the connection is to an ac line.

(e) Why is choke coil needed in the use of fluorescent tubes with ac mains? Why can we not use an ordinary resistor instead of the choke coil?

Q. Answer the following questions:(a) In any ac circuit, is the applied instantaneous voltage equal tothe algebraic sum of the instantaneous voltages across the serieselements of the circuit? Is the same true for rms voltage? (b) A capacitor is used in the primary circuit of an induction coil. (c) An applied voltage signal consists of a superposition of a dc voltageand an ac voltage of high frequency. The circuit consists of aninductor and a capacitor in series. Show that the dc signal willappear across C and the ac signal across L. (d) A choke coil in series with a lamp is connected to a dc line. Thelamp is seen to shine brightly. Insertion of an iron core in thechoke causes no change in the lamp’s brightness. Predict thecorresponding observations if the connection is to an ac line. (e) Why is choke coil needed in the use of fluorescent tubes with acmains? Why can we not use an ordinary resistor instead of thechoke coil?

Q. An electric lamp which runs at

100 V

dc and consumes

10 A

current is connected to ac mains at

150 V, 50 H z

cycles with a choke coil in series. The inductance of voltage across the choke is given as

x \times 10^{- 3} H

.Find

x

Neglect the resistance of choke.

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