1
PHYSICS
MODULE
2. ELECTRICITY
TOPIC:
2 ELECTRICITY
2.1 ANALYSING ELECTRIC FIELD AND CHARGE
FLOW
CONTENTS:
1. CHAPTER HIGHLIGHT (30 MINUTES)
2. ACTIVITY (50 MINUTES)
3. ASSESSMENT (40 MINUTES)
4. MARING SCHEME(ANSWER EY)
2
CHAPTER 2
ELECTRICITY
2.1 Analysing electric fields and charge flow
1. _____________________can be produced by rubbing an object (e.g. polytena rod)
with soft fabric.
2. The produced charge is static which is known as _____________________.
3. Sybol for the !uantity and unit of electric charge.
Sybol for the !uantity Sybol for the unit
of electric charge of electric charge" #oulob
$. Type" sybol and %alue of a unit of electric charge
Type of charge Sybol &alue of a unit ( #oulob)
'ositi%e charge (proton)
(egati%e charge (electron)
). The relationship between the total of electric charge and the aount of electric charge.
The total of The aount of The %alue of a unit
electric charge electric charge of electric charge
( *1.+ , 1-
.1/
# )
+. Example:
0hat is the aount of the electron needed to carry charge of 1 # 1
Formulae: Q ne Given: 2 3 1 # Find: n 3 1
e 3 *1.+ , 1-
.1/
#
Solution: 2 3 ne .4. n 3 2
e
3 1
1.+ , 1-
.1/
3 +.2) , 1-
15
electrons
7. 6lectric current is defined as the rate of ___________________.
3
Q 1 C
Q ne
5. Example:
7f the current which flows through a bulb within a inute is 1.) 8. #alculate the electric charge
that has flowed within a inute.
Formulae: Q It Given: 7 3 1.) 8 Find: 2 3 1
t 3 1 inute
3 +- s
Solution: 2 3 7t
3 (1.))(+-)
3 /-.- #
/. The relationship between the current flow and the electric charges.
The abo%e set up designed to show that the electric charges which flow through a conductor
produce electric current.
10. 8n electric field is an area which if entered by a charged object" it will e,perience the
__________________ which is produced by a !uantity of charge.
$
C!rrent Rate of charge flow
i.e. C!rrent Charge flow
Ti"e
Formulae:
I Q # Q It
t
Unit:
A Cs
$1
# C As
gal%anoeter
&an de
9raaff
generator
0ater tap
11. The paths of electric field of a positi%e charge can be represented by the electric force lines or
electric field lines.
12. The characteristics of the electric field line are:
(i) The lines begin fro the positi%e charge and end at the negati%e charge.
(ii) The lines do not o%erlap.
(iii) The lines repel each other.
(i%) The lines intensity represents the electric field intensity.
13. The pattern of electric field lines depends on the pattern of charged object.
(a) single spherical (positive charge) (b) single spherical (negative charge)
(c) two spherical of same charges (d) two spherical of different charges
X = neutral point
(e) a positive spherical & a negative
plat
(f) two plats of different charges
)
$
$-
*
.-
* .
%
1$. The effect of the electric field upon the charges.
(i) 8 ping.pong ball coated with conducting aterial
Step bservation !"planation
(1) # $er% &igh
$oltage source is
connected to the
plats
'1 '(
The ping)pong ball remains
motionless
#ttraction force on
the ping)pong ball
from positive plat is
at the magnitude with
the attraction force
from negative plat*
i.e. '1 = '(.
The ping)pong ball is
neutral
(() The ping)pong
ball is pulled until
it touches
negative plat
'
(i)
+hen the ping)pong
ball touches the
negative plat* this
ball will receive the
electrons and will be
charged negative.
This negativel%
charged ball will be
pushed b% the
negative plat and will
be attracted b% the
positive plat
nce the ping)pong
ball touches the
+
*
$
& .
&
$
. . . . .
&
'
(ii)
The ping)pong ball oscillates bac,
and forth between the two plats
until the $er% &igh $oltage source
is disconnected
positive plat* all of its
negative charges will
be neutrali-ed.
'urther* the ball will
be positivel% charged
This positivel%
charged ball will be
pushed b% the
positive plat and will
be attracted b% the
negative plat
The ball later will
touch the negative
plat* and the
processes will be
repeated.
(ii) 8 candle flae
Step bservation !"planation
# $er% &igh
$oltage source is
connected to the
plats
The flame is not s%mmetricall%
distributed
The flame is deflected more
towards the negative plat
The heat energ%
produces positive
and negative ions
around the candle
flame
.ositive ions which
are heavier will bring
more flame attracted
towards the negative
plat. This happens
because the positive
ions move rather
slow
/egative ions
(electron) which are
lighter will occup%
smaller flame area
;
* * *
*
.
&
&
$
.
&
&
&
Assessments
Objective Questions
1. 0f a charge of 100 2 flows through a bulb ever% ( minutes. 2alculate the current which
flows through that bulb.
# (.0 # 3 (.4 # 2 140 # 5 600 #
(. There are 4 " 10
17
electrons flow through a bulb within (0 seconds. +hat is the value
of current flow 8 ( 9iven e= 1.6 " 10
)1:
2 )
# ;0 m# 3 0.7 # 2 16 # 5 70 #
'tr!ct!re Q!estions
8. 1 <efine the following ters.
(a) 6lectric current: __________________________________________________
__________________________________________________
(b) 6lectric field: __________________________________________________
__________________________________________________
5
6lectric current is defined as the rate of charge flow.
8n electric field is an area which if entered by a charged object" it will e,perience the
electric force which is produced by a !uantity of charge.
2 Sketch the electric field lines showing the direction of the field.
(a) single spherical (positive charge) (b) single spherical (negative charge)
(c) two spherical of same charges (d) two spherical of different charges
(e) a positive spherical & a negative
plat
(f) two plats of different charges
/
$
$-
*
.-
* .
*
$
& .
=. 1 6,plain the effect of the electric field upon the charges in the following cases:
(i) 8 ping.pong ball coated with conducting aterial
(ii) 8 candle flae
1-
8nswer: 1 = 2 8
