• NCERT Solutions
  • RD Sharma
    • RD Sharma Class 12 Solutions
    • RD Sharma Class 11 Solutions Free PDF Download
    • RD Sharma Class 10 Solutions
    • RD Sharma Class 9 Solutions
    • RD Sharma Class 8 Solutions
    • RD Sharma Class 7 Solutions
    • RD Sharma Class 6 Solutions
  • Class 12
    • Class 12 Science
      • NCERT Solutions for Class 12 Maths
      • NCERT Solutions for Class 12 Physics
      • NCERT Solutions for Class 12 Chemistry
      • NCERT Solutions for Class 12 Biology
      • NCERT Solutions for Class 12 Economics
      • NCERT Solutions for Class 12 Computer Science (Python)
      • NCERT Solutions for Class 12 Computer Science (C++)
      • NCERT Solutions for Class 12 English
      • NCERT Solutions for Class 12 Hindi
    • Class 12 Commerce
      • NCERT Solutions for Class 12 Maths
      • NCERT Solutions for Class 12 Business Studies
      • NCERT Solutions for Class 12 Accountancy
      • NCERT Solutions for Class 12 Micro Economics
      • NCERT Solutions for Class 12 Macro Economics
      • NCERT Solutions for Class 12 Entrepreneurship
    • Class 12 Humanities
      • NCERT Solutions for Class 12 History
      • NCERT Solutions for Class 12 Political Science
      • NCERT Solutions for Class 12 Economics
      • NCERT Solutions for Class 12 Sociology
      • NCERT Solutions for Class 12 Psychology
  • Class 11
    • Class 11 Science
      • NCERT Solutions for Class 11 Maths
      • NCERT Solutions for Class 11 Physics
      • NCERT Solutions for Class 11 Chemistry
      • NCERT Solutions for Class 11 Biology
      • NCERT Solutions for Class 11 Economics
      • NCERT Solutions for Class 11 Computer Science (Python)
      • NCERT Solutions for Class 11 English
      • NCERT Solutions for Class 11 Hindi
    • Class 11 Commerce
      • NCERT Solutions for Class 11 Maths
      • NCERT Solutions for Class 11 Business Studies
      • NCERT Solutions for Class 11 Accountancy
      • NCERT Solutions for Class 11 Economics
      • NCERT Solutions for Class 11 Entrepreneurship
    • Class 11 Humanities
      • NCERT Solutions for Class 11 Psychology
      • NCERT Solutions for Class 11 Political Science
      • NCERT Solutions for Class 11 Economics
      • NCERT Solutions for Class 11 Indian Economic Development
  • Class 10
    • NCERT Solutions for Class 10 Maths
    • NCERT Solutions for Class 10 Science
    • NCERT Solutions for Class 10 Social Science
    • NCERT Solutions for Class 10 English
    • NCERT Solutions For Class 10 Hindi Sanchayan
    • NCERT Solutions For Class 10 Hindi Sparsh
    • NCERT Solutions For Class 10 Hindi Kshitiz
    • NCERT Solutions For Class 10 Hindi Kritika
    • NCERT Solutions for Class 10 Sanskrit
    • NCERT Solutions for Class 10 Foundation of Information Technology
  • Class 9
    • NCERT Solutions for Class 9 Maths
    • NCERT Solutions for Class 9 Science
    • NCERT Solutions for Class 9 Social Science
    • NCERT Solutions for Class 9 English
    • NCERT Solutions for Class 9 Hindi
    • NCERT Solutions for Class 9 Sanskrit
    • NCERT Solutions for Class 9 Foundation of IT
  • CBSE Sample Papers
    • Previous Year Question Papers
    • CBSE Topper Answer Sheet
    • CBSE Sample Papers for Class 12
    • CBSE Sample Papers for Class 11
    • CBSE Sample Papers for Class 10
    • CBSE Sample Papers for Class 9
    • CBSE Sample Papers Class 8
    • CBSE Sample Papers Class 7
    • CBSE Sample Papers Class 6
  • Textbook Solutions
    • Lakhmir Singh
    • Lakhmir Singh Class 10 Physics
    • Lakhmir Singh Class 10 Chemistry
    • Lakhmir Singh Class 10 Biology
    • Lakhmir Singh Class 9 Physics
    • Lakhmir Singh Class 9 Chemistry
    • PS Verma and VK Agarwal Biology Class 9 Solutions
    • Lakhmir Singh Science Class 8 Solutions

Chaitanya learning

NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12

Important Questions for CBSE Class 12 Physics Introduction to Alternating Current

December 1, 2015 by Sastry CBSE

Alternating Current Important Questions for CBSE Class 12 Physics Introduction to Alternating Current

1.Alternating Current (AC) It is the current which varies in both magnitude as well as direction alternatively and periodically.
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-1

2.Effective Value or rms Value of AC It is defined as the value of AC over a complete cycle which would generate same amount of heat in a given resistors that is generated by steady current in the same resistor and in the same time during a complete cycle.
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-2
The 70.7% of peak value of current gives effective or rms value of AC

3. Average or Mean Value of AC It is defined as the value of AC which would send same amount of charge through a circuit in half-cycle that is sent by steady current in the same time.
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-3

The 63.7% of peak value of AC gives average or mean value of AC.

NOTE In a complete cycle of AC, the mean value of AC will be zero.

4. Alternating emf or Voltage It is the emf which varies in both magnitude as well as direction alternatively and periodically. The instantaneous alternating emf is given by
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-4
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-5

Previous Years’ Examination Questions

1 Mark Questions

1.Why is the use of AC voltage preferred over DC voltage? Give two reasons.    [All India 2014]

Ans. The use of AC voltage is preferred over DC voltage because of

(i) the loss of energy in transmitting the AC voltage over long distances with the help of step-up transformers is negligible as compared to DC voltage.

(ii) AC voltage can be stepped up and stepped down as per the requirement by using a transformer.

2.The current flowing through a pure inductance 2mH is, l =(15 cos 300t) A. What is the (i) rms and average value of current for a complete cycle? [Foreign 2011]
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-2qa

3. Define the term wattless current. [Delhi 2011]
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-3qa

4. Define the term rms value of the current. How is it related to the peak value?       [All India 2010c]

Ans.  It is defined as the value of Alternating Current (AC) over a complete cycle which would generate same amount of heat in a given resistor that is generated by steady current in the same resistor and in the same time during a complete cycle .lt is also called virtual value or effective value of AC.
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-4qa

5. How much average power over a complete cycle, does an AC source supply to a capacitor?    [Delhi 2009c]
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-5qa

important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-6q
Ans.  It is defined as the value of Alternating Current (AC) over a complete cycle which would generate same amount of heat in a given resistor that is generated by steady current in the same resistor and in the same time during a complete cycle .lt is also called virtual value or effective value of AC.
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-4qa

7. The instantaneous current and voltage of an AC circuit are given by I =(10 sin 300t) A and V= (200 sin 300t) V. What is the power dissipation in the circuit? [All India 2008]
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-7qa

8. The instantaneous current and voltage of an AC circuit are given by I = (10 sin 314t) A and V= (50 sin 314t) V. What is the power dissipation in the circuit? [All India 2008]
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-7qa
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-9q
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-9qa
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-9qa2

2 Marks Questions

10.A light bulb is rated 150 W for 220 V AC supply of 60 Hz. Calculate

  • the resistance of the bulb
  • the rms current through the bulb. [All India 2012]

important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-10qa
11. Prove that an ideal capacitor in an AC circuit does not dissipate power. [Delhi 2011]
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-11qa

3 Marks Questions

important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-12q
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-12qa
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-12qa2
13. (i) When an AC source is connected to an ideal capacitor, then show that the average power supplied by the source over a complete cycle is zero.

(ii) A lamp is connected in series with a capacitor. Predict your observations when the system is connected first across a DC and then  AC source. What happens in each case if the capacitance of the capacitor is reduced?            [Delhi 2013C]
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-13qa
important-questions-for-class-12-physics-cbse-introduction-to-alternating-current-13qa2
Important Questions for Class 12 PhysicsClass 12 PhysicsNCERT Solutions Home Page

Filed Under: CBSE Tagged With: Physics Introduction to Alternating Current

LearnCBSE Sample Papers
  • Factoring Calculator
  • Rational Numbers
  • CGPA Calculator
  • TOP Universities in India
  • TOP Engineering Colleges in India
  • TOP Pharmacy Colleges in India
  • Coding for Kids
  • Math Riddles for Kids with Answers
  • General Knowledge for Kids
  • General Knowledge
  • Scholarships for Students
  • NSP - National Scholarip Portal
  • Class 12 Maths NCERT Solutions
  • Class 11 Maths NCERT Solutions
  • NCERT Solutions for Class 10 Maths
  • NCERT Solutions for Class 9 Maths
  • NCERT Solutions for Class 8 Maths
  • NCERT Solutions for Class 7 Maths
  • NCERT Solutions for Class 6 Maths
  • NCERT Solutions for Class 6 Science
  • NCERT Solutions for Class 7 Science
  • NCERT Solutions for Class 8 Science
  • NCERT Solutions for Class 9 Science
  • NCERT Solutions for Class 10 Science
  • NCERT Solutions for Class 11 Physics
  • NCERT Solutions for Class 11 Chemistry
  • NCERT Solutions for Class 12 Physics
  • NCERT Solutions for Class 12 Chemistry
  • NCERT Solutions for Class 10 Science Chapter 1
  • NCERT Solutions for Class 10 Science Chapter 2
  • Metals and Nonmetals Class 10
  • carbon and its compounds class 10
  • Periodic Classification of Elements Class 10
  • Life Process Class 10
  • NCERT Solutions for Class 10 Science Chapter 7
  • NCERT Solutions for Class 10 Science Chapter 8
  • NCERT Solutions for Class 10 Science Chapter 9
  • NCERT Solutions for Class 10 Science Chapter 10
  • NCERT Solutions for Class 10 Science Chapter 11
  • NCERT Solutions for Class 10 Science Chapter 12
  • NCERT Solutions for Class 10 Science Chapter 13
  • NCERT Solutions for Class 10 Science Chapter 14
  • NCERT Solutions for Class 10 Science Chapter 15
  • NCERT Solutions for Class 10 Science Chapter 16

Free Resources

RD Sharma Class 12 Solutions RD Sharma Class 11
RD Sharma Class 10 RD Sharma Class 9
RD Sharma Class 8 RD Sharma Class 7
CBSE Previous Year Question Papers Class 12 CBSE Previous Year Question Papers Class 10
NCERT Books Maths Formulas
CBSE Sample Papers Vedic Maths

 

NCERT Solutions

NCERT Solutions for Class 10
NCERT Solutions for Class 9
NCERT Solutions for Class 8
NCERT Solutions for Class 7
NCERT Solutions for Class 6
NCERT Solutions for Class 5
NCERT Solutions for Class 4
NCERT Solutions for Class 3
NCERT Solutions for Class 2
NCERT Solutions for Class 1

Quick Resources

English Grammar Hindi Grammar
Textbook Solutions Maths NCERT Solutions
Science NCERT Solutions Social Science NCERT Solutions
English Solutions Hindi NCERT Solutions
NCERT Exemplar Problems Engineering Entrance Exams
Like us on Facebook Follow us on Twitter
Watch Youtube Videos NCERT Solutions App