In NCERT Class 12 Physics Chapter 7, "Alternating Current," students delve into the principles of AC circuits, exploring the behavior of resistors, capacitors, and inductors under alternating voltage. Topics such as the phase relationship between current and voltage, impedance, and the power factor are discussed, with practical applications including transformers and electrical devices.
This article provides a comprehensive resource for exam preparation. It includes sample MCQs and subjective questions for CBSE and CUET, alongside downloadable PDFs of Class 12 Physics Chapter 7 MCQs and previous year questions for detailed practice of NCERT Class 12 Alternating Current.
|
NCERT Class 12 Physics Chapters
|
|
This question bank includes previous years' CUET and CBSE MCQs, along with questions curated by subject experts. Below are 5 sample multiple-choice questions (MCQs) for Class 12 Physics Chapter 7: Alternating Current. For the full set of 50 questions, download the PDF using the link provided below.
|
1. |
An ideal inductor is connected across an AC source of voltage. The current in the circuit. (a) is ahead of the voltage in phase by 𝜋. (b) lags voltage in phase by 𝜋. (c) is ahead of voltage in phase by 𝜋 /2. (d) lags voltage in phase by 𝜋/2. |
|
2. |
An inductor, a capacitor and a resistor are connected in series across an ac source of voltage. If the frequency of the source is decreased gradually, the reactance of: (a) both the inductor and the capacitor decreases. (b) inductor decreases and the capacitor increases. (c) both the inductor and the capacitor increases. (d) inductor increases and the capacitor decreases. |
|
3. |
Which of the following statements about a series LCR circuit connected to an ac source is correct? (a) If the frequency of the source is increased, the impedance of the circuit first decreases and then increases. (b) If the net reactance (XL – XC) of circuit becomes equal to its resistance, then the current leads the voltage by 45°. (c) At resonance, the voltage drop across the inductor is more than that across the capacitor. (d) At resonance, the voltage drop across the capacitor is more than that across the inductor. |
|
4. |
The selectivity of a series LCR a.c. circuit is large, when (a) L is large and R is large (b) L is small and R is small (c) L is large and R is small (d) L = R |
|
5. |
The power factor of a series LCR circuit at resonance will be (a) 1 (b) 0 (c) ½ (d) 1/√2 |
This question bank includes previous years' CBSE subjective questions (2 marks and above) without solutions, along with expert-curated questions. Below are 5 sample subjective questions for Class 12 Physics Chapter 7: Alternating Current. To access all questions, download the PDF from the link provided below.
|
1. |
An ideal inductor of (a) Calculate the rms and peak value of current in the inductor. (b) What is the phase difference between current through the inductor and the applied voltage? How will it change if a small resistance is connected in series with this inductor in the circuit? (CBSE 2020, 3M)
|
|
2. |
An ac source of emf V = V0 sin ωt is connected to a capacitor of capacitance C. Deduce the expression for the current (I) flowing in it. Plot the graph of (i) V vs. ωt, and (ii) I vs. ωt. (CBSE 2020, 2M)
|
|
3. |
An ac voltage v = vm sin ωt (vm = 310 V and f = 50 Hz) is connected to a pure capacitor of capacitance 15 F. Calculate (i) the reactance of the capacitor, and (ii) the amplitude of the current. Write the expression of current through the capacitor as a function of time. (CBSE 2023, 3M)
|
|
4. |
An ac source v = vm sin ωt is connected across an ideal capacitor. Derive the expression for the (i) current flowing in the circuit, and (ii) reactance of the capacitor. Plot a graph of current i versus ωt. (CBSE 2023, 3M)
|
|
5. |
The figure shows the graphical variation of the reactance of a capacitor with frequency of ac source. (a) Find the capacitance of the capacitor. (b) An ideal inductor has the same reactance at 100 Hz frequency as the capacitor has at the same frequency. Find the value of inductance of the inductor. (c) Draw the graph showing the variation of the reactance of this inductor with frequency. (CBSE 2020, 3M)
|
|
Chapter Name |
Sub Topics of Chapter 7: Alternating Current |
|
Alternating Current |
7.1 Introduction |
|
7.2 AC Voltage Applied to a Resistor |
|
|
7.3 AC Voltage Applied to an Inductor |
|
|
7.4 AC Voltage Applied to a Capacitor |
|
|
7.5 LCR Series Circuit |
|
|
7.6 Power in AC Circuits |
|
|
7.7 LC Oscillations |
|
|
7.8 Transformers |
NCERT Class 12 Physics Chapter 7, "Alternating Current," explains the behavior of AC circuits containing resistors, capacitors, and inductors. It discusses key concepts such as impedance, power factor, resonance, and transformers, highlighting their applications in real-world electrical systems.
This chapter is essential for understanding AC systems used in power generation and distribution. Mastering NCERT Class 12 Alternating Current enables students to solve problems related to electrical circuits and enhances their preparation for competitive exams like CBSE and CUET.
_0.jpg?null)
H inductance is connected to a 200 V, 50 Hz ac supply.
