曹營藥
頁三第張六第
日九廿月二年申戊龐買
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1454 英文中學會考試題預習專欄
物理科 (廿二)
41. Solution
Physics (22)
陸永熾-
A simple D.C. motor consists of a retangular coil of wire mounted on an armature so as te rotate between the poles of a permanent magnet. The ends of the coil are soldered to the two halves of a copper clit ring or commutator. Two carbon brushes with leads for electric aurrent are pressed alightly against the comutator by apring.
Theoretical circuit
Practical Circuit is
Z
B:
commutater
earbon brush
The action of the motor 1s due to the presence of two magnetic field that provide a cotational torque the field of the permazont magnet and the field provided by the current rlowing in the coil. The direction of the torque can easily by explained by the left-hand rule - the first three fingers, thumb, forefinger and middle finger, are set mitually at right angles to one another. If the fore finger and middle finger represent direction of the magnetic field and current respectively, the thumb shows the direction of motion offer by the fields.
The following shows the sequence of rotation:
current leading into the paper
current leading out of the paper
S
AS
unknown resistance
hesistance box
resistance wire mounted on metre mile
T: movable contact
K: kay
G: galvanom ver
The following is how vuie Instfamou
to measure the unknown resistance f
(2) The key K is pressed, current fiauss
(2) Sidg d the movable contact Talong the
ased.
resistance wire AB, until the galvanometerz
gives no deflection are measured.
(3) The lengthe Ex and
Substitution Into the follow:-
-
رینگے
la
The unknown resistance R is determinad.
ohits
8 ohms
香港仔及油蔴地兩區
<特劃】 香港中文大學教育學
大學 高福已期始招收一九六花道六九年
將建新官小
日七廿月三年八六九一曆公年七十五國民中
校舍復嫌殘舊 地官小 原日兩校 規模既小 極短楮素可向後大, 取代現有之香港仔官小及油蔴醬,而散熱機,
- 與運新宮小學之境 下,其航脊球類 邗及校友會正副瀹虢雠導學生直蹴䫈
路,就區算,連戲優曼德,再由主任離 中文大學徵聘 三師校友會合辦 质的我們,冠軍,可到者有望再長李阿帖 黄事頒發學期武獎張子軍,交通安全鬱 【竹坑政府邸 租絫新阨 近媵生四米亞 生集中行和等數百人。大會由車開。至預定時間,在 前大塔,尤以附近南 活動亦著成語,刻意,認為早九時,先通案,李穗子鐘毀整份,各生無不笑遂國 基于近年香来仔南 分赛之灘長室,及其本月二十六日認離,及主任陳志雄,頂,最後,分錢校友 有之藝校。同時,亦3之科聯實驗室 - 相當,運動,可稱勁旅。淨額光,張實,費」而,畫而學生有 湘引下 - 以岛好秩序
該開份:
見習行政助理|
郓聖诎香港
國你行巾
應符政文
八 供資助小學學翮餅在於堡之新街廣中心 四間有所用,不八門的海行 學學位,在過去一年又位於九侧中央有衍生,安全,彩腕帶大省。 六一九七一年路,可操 誠開,散活局已內領 興建一洲輝有十四至方面通淆,預料打步 ,加上四萬五千多的地點-嚓干油議題。此原因, 上 個,因爲港府計劃到市度禇計劃 計劃在近悸地 鸡證計劃,以薹青師
小學教學研討會
裕下可該見香明聘
去能智港理
院學育教大中
生新年本招開
可及期修申生學
獲格滿請可業
理月處)
期限及一年,期濓考試及格,由大
凡有志粱修者,可於毎日辦公
月十六日前受繳還,謝期概不受
慮到鋼蝘行大厦三禳致两学院辦事
申請 時間內,往九雅爾牧道六〇一號A
梁 年九月設立,由大學校務主任
中文大學教育學院於一九六
蒼松翠柏,經霜猶茂
討論 歡迎三校校友參加 題演講及中、英、算三科之分組 職待遇:月薪 四月三日假柏師學院舉行 有專 學學位,《二》有良
好之中英文程翩。
两官小徒新建 英,月台計劃消 代替現有上官小, 圄。當局爲配合此碓甚案之宮立小學,以
| 青菜造股會。
仿林中學慶祝
除此之外,九翮油織 簡陋,而且不只 之香港仔官立小學。亦比其能當立小 立小學,以轉代現有高校營舍群,和管 港仔與茷一間新型官 政經官立小學。與 此創造花樹,在一九五一年時 收容蚺婦之兒童就學,以前之子弟控
喜氣洋 採取樣揄胞,列 案亙地勢下涵要備五年歷史,跌屢經棷 面踟璱党, 陳秉進宮,戊、小學營運與中學營學之配合間題。亡、小羅王持人樹生
四十五年校慶 地之官立小學,亦將有千五開,現除一間隊聯運以來,有四— 陳具,請帶之優劣, 外中試試穎之分析,門、课本興致材間照,丁、如何待進學生學 位之姓名,職类及地 「可是说我部高級激背宫榮質專題(升中試委員會秘書何雅 地瓞篇..紅磡鶴悌裼怕立基師範學院。會議程序如下: 昨日舉行慶祝大會 全校”際文甘詞,莒、助摩我有用〔小學教育)何雅明致詞,四、教育一十三郛止。” 【特訊丷仿林巾 ¥惚悴,不論網戶研討大綱:印、小團媒桿與升中就盡頑檞夢之樣對,乙、歷年作關本,及商流產西論文。此外,並採用導師制,由各褫導師對各上,以個別離導。 一、三代表致鬥會詞,二、贊助人柏立基師筵學院院長黃千元,至一千三百一 台灣巡),五、休息,大、分組討論(分中、洪、紅三科舉行 四月六日前,具感到該院各科教學都採用先造方法,學生除在課堂上釋外,桔園 百三十六冗止。女:
|四百六十六元,年增 「城港幣計,男:一千 1千一百元,年塲五者,配陣容花上 闽傷,速閲近6 注重互相討論及外研究,學生並緻作定期寫作研究報及教育
· 例如去年終考試者一百三十三名,無償時取二十二人。 教育學院每年招生,大畢業少都相投考,但學頗有限, 該學院共有七名事任浟席,十名兼任教席,均爲中外知名 該院目前學生共二十六名,其中日校十六名,夜校十名。
三期星
撲熱盉方値述撚丙阡類破,已被列一轉下,開啟敵育工作 劣勢,故該營歷史
卸外,又有三面,而依然屹立霄鍵,於亨段困難,这就是在主流為方便無工作起見,凡有意度香港中文大學校務中太大基我低學院計劃將絲院體一致究造」,律第
一六七七號恒生銀行於
明務大道 地 两
生
十 , 在該影院怡務完畢的學生,出路樹,阿捷喜歡育工作,由
應現
小學,因皆有網室ㄤ1現于官立離校程僅有,穆同人,一本破 旺。在&甜則有完豬·歲會(北上鄉道二十四號運宮緻校友會學校) * [ 元 } 「憑南面一
封
師
S
N
5
HONGKING
(
coil is horisontal Torque is maximum, and clockwise
}
coll is vertical; no current, rotation due to inertia only.
07日
S
4 and a cuivert laterally
with cursent direction shown.
Torque maximum ang utili
clockwise
Main supply voltage
COIL Vertioga kgmaTA » no current ip wire, inertia keeps on the rotation.
Total resistance of cable - 0.16 onm Current in the sable - 15 amp
(a) Power loss in mb1
× 15 ×0.10 ww
36 watte
"Voltage drop' is cable • 15 x 0.16 volts
(b) Potential differénce between the terminais.
of motor = (240
- 237.6 volte
Power consumed = 15 x 240 atte
¥2600 watto
-
2.6 KM. Unit of power consumed - 2.6 × 5
(a) Cost in rimning the motor for 5 hours
- 2.6 x 5 x 20 - $2.60
Ane. (a) Power lost in cable is 36 watts.
(b) p.d. in the motor 18 237.6 volts. (c) It costs 2.60 dollars in running the
motor for 5 houra.
12 volts
B.af. of battery
6 ohms
- 12 volts
"Internal resistance - 6 ohms
Fotal external resistance - 6 x 8
12
う
Jhos
PHBLIC LIB
6x8+6 x 14
12 x 4 6(8+14)
14
amp.)
Currents in 6-ohm and 8-ohm resistors arej
in the proportions of à to 3
*., Currents in b-ohm resistor"=
x
B
?
Current!in: 8-ohn ́resistor--
3
14
x
7 11
Ans. The currents in 6-chm ́and 8-ohm resistors)
are 8
and 6 amp. respectively, T
Questions_for.next week).
with the help of diagram,"describe`a`moving ́coil ,ammeter and explain its action.
A moving coil ammeter of resistance. 5 ɑnma measures a maximum current of 50 milliamp. How can it be adapted to measure a maximum qurrent of) 5 amp..
L&T Describe a potentiometer and how would you use
it to compare the E.M.F.s of two cella?
£2. For a unifors metal wire, Ita erosa-anctaona)
area is throughout the same and its resistivity
the is also constant. Therefore, K =
ZAP restatance is proportional to the Length, The other factor that determines ita resistance is tenna rature.
1
The_metre bridge
-- The wire of a potentiometer is 200 am." long and has a resistance of 4.4 ohms, when a Daniel1} sell (e.m.f. - 1,1 volts) in series with a galvanometer is being tested on the potentiometeT) `wire, no current flows through the galvanometer,
when the points tapped are 129 am, apart. Find the current flowing in the potentiometer,wire.
1968
(接第六張第二頁)
英文中學會考試預習專欄
化學科 (廿二 )
besting with nitrie oxide. If a
.
王錦釗、
The gae may be distinguished from oxygen by
test-tube each of nitrous oxide and oxygen is brought into contact with a test-tube of nitric oxide, the test-tube of nitric oxide does not undergo my chemical change with nitrous oxide, but it will turn brown on contact with oxygen.
2NG+2
By experiment, 100 ... of nitrous oxide gave
100 0.a. of nitrogen
$..
i volume of nitrous oxide woula gave i volume of nitrogen
Applying Avagadro's Hypothesis, we outain 1 molecule of nitrous oxide would give 1 molecule of nitrogen
Vapour density of nitrous oxide ◄ 21 (approx.) Approx. molecular weight of nitrous oxide
- 21 ■ 2 - 42
Mol, weight of nitrogen - 14 x 2 - 28
Wt. of oxygen in 1 molecule of nitrous oxide
(approx.)
- 42 - 28 - 24
Atomic wt, of oxygen - 16
Thus molecule of nitrous oxide contains i alam of oxygen.
Therefore, the probable formula of the gas 16 N2U
Questions for next week (23)
1. How would you prepare crystalline specimens of
sodium nitrate and lead nitrate from a mixture of sodium carbonate and lead garbonate. Compare tha action of heat on these twg nitrates. State what you would observe and explain wome happens when ammonium nitrate is heated in a teat- tube, and when a glowing salint is held at the mouth of the tube.
2. How would prepare and collect e pure specimen of
nitrogen peroxide in ti a labors Lory?
Name the eroducts which are forged when nå trøgen dioxide reacts with (1) cold water, (11) het water (111) damn sulphur dioxide, (iv) burning magnesium ribbon,men snage kog
Give aqua 2ions for all the reactions you qBIGELO,