SS3: PHYSICS  2ND TERM

Magnetic Field  Week 14 Topics

Electromagnetic Field4 Topics

Electromagnetic Induction6 Topics

The Transformer5 Topics

Simple A.C Circuit4 Topics

Models of the Atom2 Topics

Radioactivity3 Topics

Half Life8 Topics

Energy Quantization3 Topics

Photoelectric Effect4 Topics

Wave Particle Paradox3 Topics
Participants 9900

Do you like this content?
Follow us
Simple Alternating Current (A.C) Generator
The a.c generator consists of:
 an armature a rectangular coil consisting of a large number of an insulated wire wound on a laminated soft iron core
 a magnetic field created by the curved poles ofÂ a horse shoe magnet or an electromagnetÂ
 two copper slip rings R_{1}, R_{2}– to which ends of rectangular coils are connected and which rotate with the armature
 two stationary carbon brushes : which are made to press lightly against the slip rings Â
An alternating voltage whose waveform is obtained above at the terminals by means of carbon brushes and slip rings
If the coil of area A rotates in magnetic field of strength B. Let the normal to the coil make an angle Î¸ with the field as shown,
Flux Î¸ through the coil is given by Ï† = ABCosÎ¸ ________(1)
If there are N number of turns in the coil, then, Ï† = NABcosÎ¸ _________(2)
If the coil turns with a steady angular velocity Ï‰ is given by
Ï‰ = \( \frac{dÎ¸}{dt} \) _________(3)
the induced e.m.f is given byÂ
E =Â \( \frac{ dÎ¸}{dt} \) _________(4)
The above equation follows from Faradayâ€™s and Lenzâ€™s laws
E =Â \( \frac{ dÎ¸}{dt} = \frac{ d}{dt} \scriptsize (NABcosÎ¸) \)Â
E = \( \scriptsize – NAB Â \normalsize \frac{ d}{dt} \scriptsize (cosÎ¸) \)
E =Â \( \scriptsize NAB sinÎ¸ Â \normalsize \frac{ dÎ¸}{dt} \) _______(5)Â Â
From equation (3) Â Ï‰ = \( \frac{dÎ¸}{dt} \)Â
âˆ´ E = NABÏ‰ sinÎ¸ __________(6), if Î¸ = 90 , then equation 6 becomes
Â E = NABÏ‰ = E_{O }___________(7)
where E_{O} is the maximum induced e.m.f which occurs when the coil is parallel to the field direction.
E = E_{O}sinÎ¸, but Ï‰ = \( \frac{dÎ¸}{dt} \), Î¸ =Â Ï‰t
Â E = E_{O}sinÏ‰ t ______________(8)
Alternating current a.c is a current which changes continually in direction while passing through a conductor
Measurement of A.C
An a.c can be measured by:
Hotwire ammeter using the heating effect of current
Moving iron ammeter using the magnetic field of current
Moving coil galvanometer to which a rectifier is attached to convert a.c to d.c
Responses