Class notes
alternating current notes
- Course
- Institution
Detailed alternating currents notes with definitions, text, images, and additional info from 9702 past papers I have completed from , all variants
[Show more]
Seller
Follow
advikasharma
Content preview
Alternating currents Alternating current – current which changes in magnitude and direction
Alternating current has sine wave characteristics
Sine wave y-axis may represent voltage or current
Peak to peak value – the difference between two peak values
I = I 0sinωt where I = value of current at any time t; I 0 = Current at amplitude; and ω =
angular frequency in rad/s
V = V 0 sinωt where V = value of voltage at any time t; V 0 = voltage at amplitude; and ω =
angular frequency in rad/s
Cathode ray oscilloscope:
Time base control – controls x axis, moving the waves closer of further apart
- 0.5ms/cm or 0.5ms/division
Y gain control – controls the y axis and hence the amplitude of the waves
- 5V/cm or 5V/division
Example –
Y- gain = 2V/cm and Time base = 5ms/cm
1. Time taken for one cycle. 5 x 4 = 20ms
2. Max voltage = 2 x 2 = 4V
3. Frequency = 1/T = 1/0.02 = 50Hz
Remember to always take exact points off the graph
, Root mean square value of an alternating current (or voltage) is the equivalent to its direct
current value that produces the same power as the alternating current (or voltage).
r.m.s. value gives the dc value
the d.c voltage (or current) is about 70% of V 0 or I 0 of alternating current
I 2 always has a positive value and is much
greater than I (green dotted lines)
I2 I2
Mean value will be , therefore r.m.s will be the root of the mean square ( ¿ so,
2 2
I = I
2
r.m.s =
√ 2 √2
Mean value of a.c. is zero. Heating occurs in a resistor connected to a.c because heating
depends on I 2 which is always positive.
Power, voltage, and current all vary with the mains supply (a.c.)
V2
Power (P) = IR = I 2 R =
R
P (a.c) = V rms x I rms
V peak I peak
= x
√2 √2
Advantage disadvantage
a.c. can be transformed to high voltages Lines must be suspended high above
so current flowing is reduced and lower ground and high-quality insulators are
power losses are incurred needed
As current flows it loses power because
of resistance and wire becomes warm
p peak
=
2
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller advikasharma. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.54. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
77254 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now