NCERT Solution Physics Class 12 Chapter 7 Alternating Current
NCERT Solution Physics Class 12 Chapter 7 Alternating Current all questions and answers. Physics Class 12 7th Chapter Alternating Current exercise solution and experts answer. As one of online learning platforms, we (netex.) are excited to offer the NCERT Solution Physics Class 12 Chapter 7. This solution is designed to help students who are looking to brush up on their physics concepts on Chapter 7 Alternating Current.
7.1)
7.4)
7.7.)
7.9)
7.11)
In case you are missed :- Previous Chapter Solution
7.18)
7.19)
7.20)
7.21)
7.22.) 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 lamp’s 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?
ANSWER-
(a) For series connections applied voltage equal to the sum of the instantaneous voltages across the series elements of the circuit but the same is not true for rms voltage. As rms voltage is different for different elements like capacitor or inductor or resistor. It may be the case that their magnitude is same but voltage across the elements may be in phase or out of the phase depending upon type of elements present in series combination.
(b)We know that induction coil works on mutual inductance. When current through induction coil suddenly brakes it changes the flux suddenly by large amount which will produce very high induced emf in the coil which in turns results in sparking in the circuit. But if capacitor is used in the circuit then this high induced voltage get stored in capacitor thereby preventing the sparking phenomenon hence the capacitor is provided in the primary circuit of induction coil.
(c) We know that for inductor, inductive reactance = ωL and for capacitor capacitive reactance = 1/ ωc
For DC supply ω = 0
\Inductive reactance = ωL = 0 and capacitor capacitive reactance = 1/ ωc =infinity
Hence for dc supply impedance of inductor is zero but impedance of capacitor is infinity hence dc supply appears at capacitor. On the other hand when ac supply of high frequency is applied impedance of capacitor become zero which will allow ac part of the supply hence ac voltage will appear across inductor L.
(d) We know that iron core has inductance (L) and zero resistance. A choke coil in series with a lamp is inserted with an iron core in the choke causes no change in the lamp’s brightness as it increases L which has no effect on dc supply. On the other hand when this scenario is tested with ac supply then definitely brightness will be reduce as iron core with inductance L will increase the impedance of the circuit as it is connected in series of the lamp.
(e) Using resistance in the series has biggest drawback of energy dissipated in the form of heat. Chock coil is used in the fluorescent lamp to reduce the current hence choke coil is used which has inductance which increases impedance of the circuit thereby reducing the current without loss of energy.
7.23)
7.25)
In case you are missed :- Next Chapter Solution
For more update, follow this page ⇒ NCERT Solutions