Section 15.1 Electric Circuit

8/14/2019 Section 15.1 Electric Circuit

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Manhattan Press (H.K.) Ltd. 1

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


Electric circuit

conditions for a bulbto glow:

power sourceclosed circuit


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Electric circuit


Open circuit

emove randomly-

switch isopen

no electric currentproduced

battery

copper

wires

light bulbremains unlit


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Electric circuit


Closed circuit

emove in one direction-

switch isclosed

electric currentproduced

battery

copper

wires

light bulbglow


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Electric current


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


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



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Measuring electric current


-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



+ terminal of battery

+ terminal of ammeter

ammeterlight bulb


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Typical currents in some electrical appliances



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


Circuit diagram represent real circuit connection for convenience


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Circuit diagram


Circuit symbols for some electrical components

battery light bulb switch


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Circuit diagram


ammeter voltmeter


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Circuit diagram


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


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.



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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



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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



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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



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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



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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.


Fig. 15.7 Fig. (a)

Section 15.1 Electric Circuit

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