section 15.1 electric circuit
TRANSCRIPT
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Section 15.1Section 15.1
Electric circuitElectric circuit
Section 15.1Section 15.1
Electric circuitElectric circuit
Electric currentElectric current
Circuit diagramCircuit diagram
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Electric circuit
15.1 Electric circuit (SB p. 37)
In modern cities
like HK
Go to
Discussion 1Discussion 1
demands huge amount of electricity
Go to
QuizQuiz
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a conducting path that electric charges flowthrough
Electric circuit
15.1 Electric circuit (SB p. 38)
Electric circuit
conditions for a bulbto glow:
power sourceclosed circuit
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Electric circuit
15.1 Electric circuit (SB p. 38)
Open circuit
emove randomly-
switch isopen
no electric currentproduced
battery
copper
wires
light bulbremains unlit
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Electric circuit
15.1 Electric circuit (SB p. 38)
Closed circuit
emove in one direction-
switch isclosed
electric currentproduced
battery
copper
wires
light bulbglow
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Electric current
15.1 Electric circuit (SB p. 39)
Electric currentbetween the dome& earth
flow of electric
charges
dome
earth
socket
light-beam
galvanometer
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conventional current
electron flow
Electric current
15.1 Electric circuit (SB p. 39)
CAL
Workshop 1
Current
http://cal/E-SimPhy_402.exe -
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t
Q
I=
=
i.e.
takenTime
flowchargeofQuantity
currentElectric
unit: ampere (A)
electriccurrent (I)
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quantity of
charge (Q)
time (t)
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Electric current
15.1 Electric circuit (SB p. 40)
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Measuring electric current
15.1 Electric circuit (SB p. 40)
-1sC1A1 =-1-3 sC10re)(milliampemA1 =
-1-6 sC10re)(microampeA1 =
ammeter milliammeter microammeter
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Measuring current through light bulb ammeter connected in series with light
bulb
Thinking 1Thinking 1
Measuring electric current
15.1 Electric circuit (SB p. 41)
+ terminal of battery
+ terminal of ammeter
ammeterlight bulb
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Typical currents in some electrical appliances
Measuring electric current
15.1 Electric circuit (SB p. 41)
Electrical appliance Typical current
Electric water heater 14 A
Air conditioner 10 A
Hair dryer 3 A
TV set 0.8 A
100 W light bulb 0.5 A
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Circuit diagram
15.1 Electric circuit (SB p. 41)
Circuit diagram represent real circuit connection for convenience
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Circuit diagram
15.1 Electric circuit (SB p. 42)
Circuit symbols for some electrical components
battery light bulb switch
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Circuit diagram
15.1 Electric circuit (SB p. 42)
ammeter voltmeter
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Circuit diagram
15.1 Electric circuit (SB p. 42)
resistor rheostat potential divider
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Class Practice 1:Class Practice 1:Fig. (a) shows an electric circuit. Draw its circuit diagram in
Fig. (b).
Ans
wer
15.1 Electric circuit (SB p. 42)
Fig. (a)
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To section 15.2
http://e-ch15_02.ppt/http://e-ch15_02.ppt/ -
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QuizQuiz
1. When you switch on a lamp, which of
the following is true?Answe
rB. The current flowing out of the light bulb is
equal to that into it.
15.1 Electric circuit (SB p. 36)
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Quiz (Cont)Quiz (Cont)
2. In a classroom, when a fluorescent
tube fails, the other fluorescent tubesstill light up. In which circuit are they
connected? Answer
B. Parallel circuit
15.1 Electric circuit (SB p. 36)
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Quiz (Cont)Quiz (Cont)
3. When you connect two identical light
bulbs A and B with a battery as
shown, which of the following is true?Answer
C. Bulb A and bulb B have the
same brightness. Return to
TextText
15.1 Electric circuit (SB p. 36)
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Discussion 1:Discussion 1:
Which of the following can you use to light up alight bulb? Discuss with your classmates.
A. a light bulb and two connecting wires
B. a light bulb and a dry cell
C. a light bulb, a dry cell and two connecting
wiresC Ans
wer
15.1 Electric circuit (SB p. 37)
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Discussion 1: (Cont)Discussion 1: (Cont)
Explain briefly why the light bulb lights up.
In a closed circuit, the dry cell provides a voltage
to drive a current passing through the light bulb.
Return to
TextText
Ans
wer
15.1 Electric circuit (SB p. 37)
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Thinking 1Thinking 1
If the positions of the ammeter and lightbulb in Fig. 15.7 are exchanged (Fig. (a)),
what happens to the current in the circuit?Ans
wer
Return to
TextText
The currents are the same. Since there is onlyone path for the current to flow, the value of
the current is the same in the whole circuit.
15.1 Electric circuit (SB p. 41)
Fig. 15.7 Fig. (a)