- Online Test Series
- Final Revision Module (3 Books)
- 5 Mock Tests
- 5 Diagnostic Tests
- 15 Practice Tests
- Sample Papers With Solutions
- Past Year Papers With Solutions
- Ask The Expert
- On Call Mentorship
Chapter Cover: Section A - Average and RMS value of Alternating Current
1. ALTERNATING CURRENT
Until now, we have studied only circuits with direct current (dc) which flows only in one direction (as shown in figure I and II). The primary source of emf in such circuit is a battery. When a resistance is connected across the terminals of the battery, a current is established in the circuits, which flows in a unique direction from the positive terminal to the Negative terminal via the external resistance.
But most of the electric power generated and used in the world is in the form of alternating current (ac), the magnitude of which changes continuously with time and direction is reversed periodically (as shown in figure III & IV)and it is given by
i=i0sin (ωt + ϕ)
Here i is instantaneous value of current i.e., the magnitude of current at any instant of time and i0 is the maximum value of current which is called peak current amplitude and the current repeats its value after each time interval T = as shown in figure, This time interval is called the time of period and ω is angular frequency which is equal to 2π times of frequency f.
The current is positive for half the time period and negative for remaining half period. It means that the direction of current is reversed after each half time period. The frequency of ac in India is 50 Hz.
An alternating voltage is given by
V=V0 sin (ωt +ϕ)
It also varies alternatively as shown in the figure (b), where V is instantaneous voltage and V0 is peak voltage. It is produced by ac generator also called as ac dynamo
Ac Circuit: An ac circuit consists of circuit element i.e., resistor, capacitor, inductor or any combination of these and a generator that provides the alternating current as shown in figure. The ac source is represented by symbol in the circuit.
2. AVERAGE AND RMS VALUE OF ALTERNATING CURRENT
2.1 Average current (mean current) As we know an alternating current is given by
i= i0 sin (ωt + ϕ) …… (1)
The mean or the average value of ac over any time T is given by
Using equation (1)
In one complete cycle, the average current
Since ac is positive during the first half cycle and negative during the other half cycle so iavg will be zero for long time also. Hence the dc instrument will indicate zero deflection when connected to a branch carrying ac current. So it defined for either positive half cycle or negative half cycle.
Chapter Cover: Section A - Flux, Faraday’s law, Lenz’s law
1. MAGNETIC FLUX
2. FARADAY’S LAE OF ELECTROMAGENTIC INDUCTION
3. LENZ’S LAW
4. CALCULATION OF INDUCED EMF
By learning in meritnation I got B2, but by learning topper learning I got A1... so which is the best. This is awesome to learn and easy to study science. At 1st term I got B2 but at 2nd term I got A1.
Manoj Vijay CBSE class IX
Excellent Faculty! I have been studying from topperlearning.com since Class IX and have consistently scored above 90% in my these 4 years.I studied throughout nights to achieve my goal.Moreover, becoming Rank 1 on topperlearning boosted my confidence to high skies.Thank you topperlearning, without you I would not have been able to score 91.2% in Class XII Boards(2015) and CGPA 9.8 in my Class X Boards(2013). Hope that topperlearning will continue to help students throughout India, creating a brighter future for them. Regards, Vivek Saahil
Vivek Saahil CBSE class XII Science
I like topper learning because I can understand the level I have prepared for my subject and study better.
Mohanapriya Saravanakumar CBSE class X
Topperlearning is really a very good helping tool. Every time I had doubts related to any concept in PCM I posted it and immediately my problem was solved. It also helped me in scoring good ranks in competitive exams too. The topper faculty is very good. The teachers explained each and every concept in depth. My favourite teacher is Physics teacher
Sahibdeep Singh Sodhi CBSE class XII Science
We all know that audio-visual medium is a better way of explaining and educating the students. It not only makes learning fun but also gives the message more clearly and precisely. Topper is a very good amalgamation of good teaching and good learning methods.
Sonia Malik, Professor
VV DAV School, New Delhi class ALL Class
Queries asked on Sunday and after 7 pm from Monday to Saturday will be answered after 12 pm the next working day.