A level Physics 9701 Alternating current 9702 Summary Notes

Alternating Current
Physics

, Alternating Current
An alternating current (a.c) has a changing direction and magnitude with time.

Direct Current (Steady d.c)
A constant (steady) direct current has constant magnitude and flows in only one direction.

There are two types of alternating currents:
1. Sinusoidal a.c
2. Rectangular/square a.c


I


I0 Sinusoidal a.c


I>0

0.01s
T =0.02s
I<0

-I0

f = 50 Hz
1 1
T= = = 0.02 s
f 50
Current changes direction every 0.01 s.
I
rectangular/square a.c
I0

|
T t

-I0

1 cycle

a.c source
I


I>0 I>0 T/2
T T
from 0 to I<0
2

T
I < 0, from to T
2




2