Physics - Summary (IEB Matric)

ELECTRIC CIRCUITS
CURRENT = the rate of flow of charge

C- MF = the total energy supplied per Coulomb of charge I
the battery
, =
by
t

1 A = 1000mA



RESISTANCE = a materials opposition to the flow of

electric current
C- Ill IN SERIES

Resistance → Ohm r R = ¥

OH MI LAW = current
through a conductor is directly
proportional to the potential difference across the conductor

at constant temperatures



✓ = 1. R



OHMIC CONDUCTORS
✓f -
VI

1,5 t 115 t 1,5 5. V DV
gradient
=
4 , =
-



D1
(f -
Ii

POTENTIAL DIFFERENCE = the work done per unit .

positive charge voltage
DV
CV )
w
-

✓ =
Q •

D l
open switch

°
current CA )

If the resistance of a conductor does not vary with current




NON -
OHMIC CONDUCTORS


CURVE
①
voltmeter will read the emf of the battery
← 9 resistance
VOLTAGE
(V)
TERMINAL POTENTIAL DIFFERENCE



voltmeter reads ← constant resistance
←
terminal potential
difference
CURRENT ( A)

as one increases the other increases to a larger extent




RESISTORS

Id Rt constant voltage
to the
→ current is inversely
proportional resistance




FACTORS AFFECTING RESISTANCE

length ( longer TR ) material type ( goYd ; nickel )
thickness ( thicker NR ) temperature ( 9 temp = MR )

, RESISTORS IN SERI ft

Rs = Ri t Rz t . . .




RESISTORS IN PARALLEL

l
l
=
I
-
t - . . .



R' R2
Rp
1. I 31 t Br = 61


RTs -
- f tf
= 31
→




30
I -
3 Rtp = To t
SFO
] = 25
→




I a -

Rtp = ft ta tf t



15¥ It I =
3,71




LT
'

I - 6 2 tf'T t t
z t

To tot )
=
6 , 84
→

ENERGY → j

w = Pt

electrical power dissipated in a device is equal to the PRELIM QUESTION
product of the potential difference across the device and
15 to dry hair for 5
min
days , et Kom = 50C 1kWh
the current flowing through it
cost = 93,75C


W = VI t w = 12 Rt w =
¥ t cost = KW x h X
' O'
tlkwh

93,75 = KW X 1,25 X 50


POWER = the rate at which electrical
energy ( W) is 93175 i KW x 62,5
converted to other forms of energy in an electric
5 1000
circuit
KW = I , X


W = 1500 W


Wt
-


p =



* is ÷ 60 =
0,25 X 5
✓2
p 12 R
p VI = P I 1,25g
= = =




cost =
power rating of appliance ( in KW ) x time used ( hrs ) x price of kWh

convert power → KW

costs KW .
h . COSY kWh
TOTAL → 97425,54C ÷ 100 R 974,26
kWh of
=
= Unit energy -


→ KW ÷ 1000
W

l TV : cost =
( 0106 X 7 X 61 ) x 30


=
768 ,
6C
-




2 GEYSER i cost =
( 2,2 X 24 X b '
) X 30


=
96624C
-


3 LAPTOP cost =
( 0,012 X 1,5 X 61 ) X 30
per kWh
:
Colt = 61C 30 days
=
,32 94C
-