NCERT Solutions Class 12 Physics Chapter 7

NCERT Solutions Class 12 Physics Chapter  7 Alternating Current 

The NCERT Solutions Class 12 Physics Chapter 7 will guide students to understand the concepts and solve questions appropriately. Class 12 Physics Chapter 7 NCERT Solutions are prepared by the subject experts at Extramarks. All answers are explained clearly in simple language while preparing the solutions, and all the guidelines given by CBSE have been kept in mind

CBSE or Central Board of Secondary Education is the most preferred educational board among schools. It covers all topics required to understand the concept clearly and thoroughly. The  NCERT Solutions Class 12 Physics Chapter 7 act as a helping hand for students to learn the subject effectively. 

Key Topics Covered In NCERT Solutions Class 12 Physics Chapter 7 

Chapter 7 Physics Class 12 explains the concept of Alternating current, its properties and use cases, a vital sub-topic under the Electromagnetic Induction unit. Students can expect questions on this topic in first term examinations. To score good marks, students may refer to NCERT Solutions Class 12 Physics Chapter 7. 

Following are the topics covered in NCERT Solutions Class 12 Physics Chapter 7 

A brief of the topics covered in NCERT Solutions Class 12 Physics Chapter 7  is below.

Topic 7.1 Introduction

Alternating current (AC) is an electric powered current that periodically reverses direction and adjusts its magnitude constantly with time, in contrast to direct current (DC), which flows best in a single direction.

Topic 7.2 AC Voltage Is Applied to a Resistor

To have a sinusoidal alternating current, we want to have an AC voltage supply because the current is at once proportional to voltage. An AC generator or AC dynamo may be used as an AC voltage supply.

Voltage V(t) is applied across resistance R. V(t) is sinusoidal voltage with peak Vm and time period T.

T=1f=2

Where f is frequency and ω is the angular frequency. This kind of circuit is a purely resistive circuit. According to Kirchhoff’s law –

v(t)=Ri(t)

i(t)=v(t)R

i(t)=Vmsin(t)R

im=VmR

i(t)=imsin(t)

Here voltage and current have equal frequency, and each is in a similar phase.

The average current value may be located out with the aid of summing over the whole change inside the voltage and dividing it using the number of instances we do the measurements. 

I.e iavg=0

Over a cycle, the average value of AC current is 0 because, in the 1st half of the time, the current is positive and in the second half, the current is negative.

Root Mean Square Value of Current, i.e. irms=im2

Topic 7.3 Representation of AC Current and Voltage through Rotating Vectors or Phasors

The projection of the phasor at the vertical axis represents the value of the quantity. For example, inside the case of a current or a vector phasor, the projection of the phasor at the vertical axis, given via means of vmsinωt and imsinωt, respectively, offers a current value or voltage value. 

Topic 7.4 AC Voltage Applied to an Inductor

It implies an AC circuit composed only of an inductor of inductance L linked to an AC supply. The AC voltage throughout the supply is V = Vm sin(t). The converting current output of the AC supply offers a returned emf inside the coil of magnitude that’s given via the means of VL = L di/dt.

Topic 7.5 AC Voltage Applied to a Capacitor

When an alternating voltage is carried out throughout a capacitor, the current leads the voltage via a phase angle of ninety degrees. This approach oscillates 1 / 4 of the cycle before the voltage.

Topic 7.6 AC Voltage Applied to a Series LCR Circuit

A chain LCR circuit is connected to an AC supply. The voltage of an AC supply is V=Vmsinωt. Potential distinction throughout the ends of capacitor =qC and potential distinction throughout the resistance ends =IR.

Topic 7.7 Power in AC Circuit: The Power Factor

Power factor (PF) is the ratio of running power, measured in kilowatts (kW), to apparent power, measured in kilovolt amperes (kVA). Apparent power, additionally called demand, is the degree of the quantity of power used to run equipment and devices all through a certain period. It is observed with the aid of using multiplying (kVA = V x A).

Topic 7.8 LC Oscillations

The LC Oscillator employs a tank circuit (comprising an inductor and a capacitor) to offer tremendous vital comments to preserve oscillations in a circuit going. 

Working of an LC Oscillator:

• When a completely powered capacitor is connected to a de-energised inductor, the capacitor gets all the circuit’s energy while the inductor receives none. Let’s name the energy saved inside the capacitor (electrical energy) UE and the magnetic energy saved inside the inductor (UB).
• Current flows from the capacitor to the inductor, energizing the inductor and discharging the capacitor. The inductor’s energy starts to evolve to rise simultaneously as the capacitor’s energy falls. The bars underneath the circuit diagram display that 1/2 of the energy saved in an inductor is equal to 1/2 of the energy saved in a capacitor, indicating that the capacitor has transferred 1/2 of its energy to the inductor.
• All of the capacitor’s energy will now be transmitted to the inductor as quickly because the capacitor is drained. As a result, a vast quantity of electrical energy is converted to magnetic energy.
• Because the capacitor has been absolutely drained and the inductor has been absolutely energized, the inductor will now start to charge the capacitor in the same direction because of the current. The present state of the circuit is depicted in the fourth diagram. As a result, 1/2 of the inductor’s energy has been transferred to the capacitor.
• Finally, the capacitor may be absolutely charged once more, and the inductor may be activated. On the alternative hand, the capacitor will now have its polarity reversed. As a result, if the current inside the circuit begins to move once more from the capacitor, it’ll flow in the opposite direction. We might also say that the primary 1/2 of the AC cycle has ended, and the second 1/2 has started because the current inside the circuit now has an opposing flow of current.
• As a result, each capacitor and the inductor may be charged two times for the duration of the cycle.

Topic 7.9 Transformers

These are used to increase or decrease the voltage of alternating currents. A transformer includes coils of wire wound on a metallic core. An alternating voltage is carried out to at least one coil (the first coil). This causes a changing (alternating) magnetic area to be installed inside the core.

List of NCERT Solutions Class 12 Physics Chapter 7 Alternating current 

Click on the below links to view NCERT Solutions Class 12 Physics Chapter 7

• NCERT Solutions Class 12 Physics Chapter 7: Exercise 7.1 
• NCERT Solutions Class 12 Physics Chapter 7: Exercise 7.2 
• NCERT Solutions Class 12 Physics Chapter 7: Exercise 7.3 
• NCERT Solutions Class 12 Physics Chapter 7: Exercise 7.4 
• NCERT Solutions Class 12 Physics Chapter 7: Exercise 7.5
• NCERT Solutions Class 12 Physics Chapter 7: Exercise 7.6 
• NCERT Solutions Class 12 Physics Chapter 7: Exercise 7.7
• NCERT Solutions Class 12 Physics Chapter 7: Exercise 7.8 
• NCERT Solutions Class 12 Physics Chapter 7: Exercise 7.9

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Key Features of NCERT Solutions Class 12 Physics Chapter 7

The key features of the NCERT Solutions Class 12 Physics Chapter 7 offered by Extramarks include

• Detailed explanations for each topic under chapter 7 Physics class 12
• Curated by Subject Experts in respective fields
• Easy to understand and simple language 
• Answers are written by giving importance to the weightage. 

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