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?
a)
The applied voltage will be equal to the average sum of the instantaneous voltage across the series elements of the circuit and it will be true for any ac circuit. But, in the case of rms voltage the voltages across different elements may not be in phase.
Thus, the statement is not true in the case of rms voltage.
b)
When the circuit is broken, a high induced voltage is used to charge the capacitor and the capacitor is used in the primary circuit of an induction coil to avoid sparks in the circuit.
c)
In the case of dc signals, the impedance of an inductor ( L ) is negligible but the impedance of a capacitor is very high. So ,the dc signal will appear across capacitor ( C ) .
In the case of an ac signal of high frequency, the impedance of an inductor ( L ) will be high and the impedance of a capacitor ( C ) will be very low. So, an ac signal of high frequency will appear across inductor ( L ) .
d)
The lamp will glow dimly when an iron core is inserted in the choke coil that is in series with a lamp connected to the ac line and this is because the iron core and the choke coil increases the impedance of the circuit.
e)
The choke coil reduces the voltage across the tube without wasting much power. So, the choke coil is needed in the use of fluorescent tubes with ac mains.
An ordinary resistor wastes power in the form of heat so, an ordinary resistor cannot be used instead of a choke coil in the use of fluorescent tubes with ac mains.
a)
The applied voltage will be equal to the average sum of the instantaneous voltage across the series elements of the circuit and it will be true for any ac circuit. But, in the case of rms voltage the voltages across different elements may not be in phase.
Thus, the statement is not true in the case of rms voltage.
b)
When the circuit is broken, a high induced voltage is used to charge the capacitor and the capacitor is used in the primary circuit of an induction coil to avoid sparks in the circuit.
c)
In the case of dc signals, the impedance of an inductor
In the case of an ac signal of high frequency, the impedance of an inductor
d)
The lamp will glow dimly when an iron core is inserted in the choke coil that is in series with a lamp connected to the ac line and this is because the iron core and the choke coil increases the impedance of the circuit.
e)
The choke coil reduces the voltage across the tube without wasting much power. So, the choke coil is needed in the use of fluorescent tubes with ac mains.
An ordinary resistor wastes power in the form of heat so, an ordinary resistor cannot be used instead of a choke coil in the use of fluorescent tubes with ac mains.
