 Class 12th Physics Alternating Current. NCERT Notes CBSE 2023

# Alternating Current Class 12 Notes # Chapter 7 Alternating Current

In this article, students can find NCERT notes for AC power. It is not only important to score well in board exams but also a necessary chapter for entrance exams. Therefore, it is important to master these concepts in order to perform well in the exams. Practicing NCERT questions will help students understand the correct approach to answering questions in exams.

CBSE class 6 chapter 11 talks about the AC voltage applied to the rheostat, the power in a purely resistive circuit, the mean value of a sine function, and the average value of the square of the sine and sine functions. , an average square of alternating current, and many others. Students must practice questions in the text provided by Vidyakul to do well in exams. Continue reading this article to know about NCERT Physics Grade 12 Chapter 7 notes.

### Points to Remember

Below-mentioned are some of the important points to be remembered from Chapter 7 of Class 12 Physics.

• Phasor: A phasor is a vector that rotates about the origin with angular speed ω. The magnitude of a phasor represents the amplitude or peak value of the quantity (voltage or current) represented by the phasor.

• LC Oscillation: A circuit containing an inductor L and a capacitor C (initially charged) with no ac source and no resistors exhibit free oscillations. The energy in the system oscillates between the capacitor and the inductor, but their sum or the total energy is constant in time.

• Transformer: If the secondary coil has a greater number of turns than the primary, the voltage is stepped-up (Vs>Vp) This type of arrangement is called a step-up transformer. If the secondary coil has turned less than the primary, we have a step-down transformer.

• Resonance: An interesting characteristic of a series RLC circuit is the phenomenon of resonance. The circuit exhibits resonance, i.e., the amplitude of the current is maximum at the resonant frequency, ω0=1LC√.

• AC Voltage Applied to a Resistor: An alternating voltage v=vm sinωt applied to a resistor R drives a current i=im sinωt in the resistor, im=vmR. The current is in phase with the applied voltage.(ii) For an alternating current i=im sinωti=im sin⁡ωt passing through a resistor  R R, the average power loss PP (averaged over a cycle) due to joule heating is (12)i2mR12im2R.

### Topics and Sub-topics

NCERT Physics Grade 12 Chapter 7 is very interesting. Students who regularly practice questions and follow concepts can easily solve problems. For your convenience, please watch the NCERT Grade 12 Chapter 7 Physics learning video provided by Vidyakul. As students practice the questions, they will develop speed and accuracy in solving any type of problem.

We have provided a list of topics covered in chapter 7 of CBSE Grade 12 Physics.

 Sr. No Topic Name Description 1 AC Voltage Applied to a Resistor 2 Representation of AC Current and Voltage 3 AC Voltage Applied to an Inductor 4 AC Voltage Applied to a Capacitor 5 AC Voltage Applied to a Series LCR Circuit 6 Resonance 7 Power in AC Circuits 8 Transformer 9 LC Oscillations

### Few Important Questions

• A 100 Ω resistance is connected in series with a 4 H inductor. The voltage across the resistor is, VR = 2.0 sin(103t) V. Find the expression of the circuit current.

The circuit current is 0.2 sin(1000 t) mA.

• A 100 Ω resistance is connected in series with a 4 H inductor. The voltage across the resistor is, VR = 2.0 sin(103t) V. Find the inductive reactance.

The inductive reactance is 4 × 103 Ω.

• A 100 Ω resistance is connected in series with a 4 H inductor. The voltage across the resistor is, VR = 2.0 sin(103t) V. Find the amplitude of the voltage across the inductor.

80 V is the voltage across the inductor.

### Practice Questions

1. A 5000 V, 70 Hz ac supply s connected to a 500 Ω resistor

1. Define the net power consumed over a full cycle (a)

2. Find out the RMS value of the current

2. (a) What is the RMS voltage if the peak voltage of an ac supply is 600 V?

(b) What is the peak current if the RMS value of current in an ac circuit is 40 A?

3. 500 V, 60 Hz ac supply is connected to a 55 mH inductor. Determine the RMS value of the current in the circuit.