1976-05-27 — Page 19

育教僑華 頁三第張五第日九廿月四年辰丙窟夏 WAH KIU YAT PO

報日僑華

四期星

中學會考物理科題解

The p.d. between V is

AB emf. of

p.d.

(三)

AB

·何輝明

the cel the 8

resistor

(0.1)8

1.2V

Therefore

RAB

V = AB

= 1252 Ans. 1.

AB

中學會考中國語文(三)試卷題

歐用自己的之间,把下面一群體次,仍成語體康寫D140字的

忍龙用补票方法鎏烙比氫法桐凼了。蠻鞴又馋,能踱卫多心训;或用齋戒

骝纖、榨擗尬妈睡和鹿,将譭胪呶“此外,還犴人工培糁煤用和分軀的方法,接蹈 辔候成功了i赟可以隨戆把一黻鸞諜分成缵小章,第一小事記上一個蜂沿,谑槛憷

蜜瘦身的口路到一些佛紙鶴:懷煺的幼蟲飛出了,民炸死亡。而且一個榮止了,俱

止邐機缚弥辘,否則需輔鹹期距不寇妙悭器的。

品

(二)就轉下面一能实战就能练酒體文

(1).足縣白光加上比署的間輪。

3)成龍虹斷學,應越劇綁發腫的滅要,把战中的鹦鹉:助力

的補-

: 一完整的熘劇

个绶網絡觀牆,週如上:「鄉下)

夏之不公義並,但之不能證其防

(2)

WEB

纽康山,並留不驟。

加。

300

計劃。試蜜‧蘇繡的體點!我啮小锪炬燃!「礬網」、「棋的歌溦小

Section C - Magnetism, Electricity.

& Atomic Physics

5. (a) Measurement of the unknown

resistor Z.

Rz

-p.d. across Z

current passing through

/ Reading of the voltmeter

coinected directly in parallel with Z'

Reading of an ammeter

connected directly in series with Z

(i) Method used in figure 7 cannot give an accurate answer, because the reading of the voltmeter is not only the p.d. across Z, but also the p.d. of the ammeter.

(ii) In the same way, figure 8 also.

carinot give an accurate.

answer, because the reading

of the ammeter is not only the current passing through Z, but also the current passing through the voltmeter.

(iii) There will be no change at

all.

Due to the equivalent. 'resistance of the whole

circuit is increased, the current passing through the ammeter will be lowered. Applying Ohm's law

The .d. across the unknown. resistor 2 will be dropped. down too. Therefore the value of Z will be no change

(iv) Method used in figure 7 is

better. It was because the ammeter is an electrical instrument of low resistance, and the p.d. across the.. ammeter is neglected. The voltmeter in figure 8. shares the main current equally with the resistor Z. This greatly reduces the accuracy.

(b)

18.52

125

852

(i) Power dissipated

by the 8l resistor)

IR

= 1.V.

(0.1)28 =0.08W-Ans.

(ii) Let the equivalent resistance

of the branches PQ and RS be

RAB

(iii) Let the current passing

through the branch RS be:

IRS

VRS

IRS

ARS

RRS

1.2

=0.04A.

124 187

Therefore the current. passing. through the branch PQ will be (0.1 -

日七廿月五年六七九一公年五十六國民籲中

(b)

third cases, the acceleration.

of the mamet is smaller than

That is to say, part of

g.

the P.E. of the magnet is converted into electrical energy in the copper ring. There is no induced current in second case, therefore: the manet falls-with the sane gravitational accelera- tion.

The current is .There is en flowing: from pt. A to pt. B.

0.04)=0.06A

RFQ

VPQ AB IPQ

1.2

0.06

(c)(i)

2057

52 -- Ans.

(iv) If there is no change in the

readings of the ammeters A and Ay, that is to say, there is no current passing through the key K.. F. And. the potential of pt. C is equal to the potential of pt. D.

This is the case of Wheatstone's Bridge

Therefore 5 x + y = 20

Solve for x and y

x=82

y = 1252

Ans.

It is short-circuited by K., and K, the current will bé just flowing through: resistor y and resistor of 18 2 only. Therefore the reading of ammeter A. will be zero.

6.(a)(i) The magnet

is just entering the ring;

(ii) There is

no induced / current in: the ring

when the

magnet is half way

through it.

(iii) The magnet

hes just passed completely. through: the ring.

Direction of the ind. I

no

·ind. I

Direction. of the ・ind. I

Len's law follows directly from the principle of. conservation of energy..

Therefore, in the first and

neutrd feint

(ii)

neutral print

a.c. flowing through the wire.

Current in wireA is down- ward

Current

in vire B is upward

Currents in the vires A. andy are: both down=" warde

(a)(i) There are energy losses

in a common transformer, such as heat lost in the coils, eddy current.in. the core and non-ideal core design.

And, in an ideal trans- former (ie. 100% efficiency)

Primary

Secondary

paver input). power: output

IqVg

(2A)(110V) = 12/(220V).

= 1 A

Therefore, the output current must always be less than 1 A.

(ii) An alternating current

(a.c.) in the primary coil will set up an alternating mametic flux. in the laminated core and, therefore, induce an alternating eim.f. in the secondary coil.

But a steady d.c. supply: will not give any change of magnetic flux, and there will be no induced e.m.f. in the secondary coil.

END

巨風偵驚懸刺緊公歐 片趣探險疑激張司洲

米

高

「群倫蛇賊

丹主角 女主角

梨妮*

活妲

主巨天闹 演王大

華聲

单

曾弄尖旺越ㄩㄝ

神

茶

戒佰謀殺領富

?恭出謂何

?打欠行五謂何

?子妻王龍作謂何

銀搬盡韻拈惹南下離皇風 幕上量事花草的江宮帝流

記遇奇皇隆乾

永英明樂亞港娛關倫明文

星華宮京聲月

洲活车樂翠敦珠華

琅明先點 番始天映半一!

土晚後

錯請會最 過勿天後

∵片色肉性越藏公司 *王惭感感多出洲

艾

妞曼

-集潁一

角主女案上妞受

桃絲莉姬

作之阻大相色牲

我中夜 艷,糖 臭賽女 舞脫會

受

害追鉅尋

命踪女

一、快献大熊天服。 照片爭戰激鹣彍無:

戰爭壘炮 R

:

線三禾嘉

遲拳獨變棍一

天。步萬。枝

加特新京 - 入别品都、咳

嘉麥

場夜午晩後涯走洪化千光

*專武情出公先

∵剛打風品司鐐

A

炭弩鑑年港香 'o

1976

格粵 外語

年

傳對 神白

萱兒

劉氏兄弟以真面目作招牌

洪拳眞功夫銀幕初放異彩

異牌