頁二第張四第日十二月四年已歷夏 WAH KIU YAT PO
英中會考物理科答案(續)陸永熾
報日僑華
三期星 日四月六年九六九一公年八十五國民華中 育教僑華·
Section D
„(a)(a) The high tension battery sets up a strong
electric field between the point A and the baltymi
(11) When the strong field breaks down the
insulation of the air between A and the belt, electrons flow from the point A to the belt. whence they are carried up to the sphere
therefore placed in series with the galvanometer to protect it by limiting the current. Once the balance point has been located it is. shorted out by closing the key K, and the final adjustment is then made to a maximum sensitivity.
(c) When the resistances are in series:
121.
中中會考經濟及公衆事務科試題
一號將下列子灣留括弧内正確答之號取於右邊適當欄內。
(A)地方法完判城犯人之利明般点不得超過(D)五年·
(A)
(8)太港蔬米之主要來消息(全泰國和中國大
(B)
MAHOTAUH).
(C)本田左之魚類可供本地消費者,達百分之四 向天抗;周六十五)。
(C)
(D)船版炎水调之站 生物(一百億加能;3三
(B)椒忠之公司,其名樣息
媒版 有限公司,淘東亞少織有限公司;3香津市珠 展有限公司)。
E.M.F. of the cell-12 volta Internal resistance of cell External resistance.
Current in the circuit
1 onm
2+2
4 ohms
12
(F)慈山新可智展品(十五;2十七萬;3
4.
(G)蔬暂桃是(1房線協會;回徙源傘燕萬;3县宇
建設電監會)所提
(H)獅子山娜(三千五百二恹;
「三十五呎;2六千百三十五天)。
(G)
2四千六百
CHO.
CTS
(1) BALRZESZOWŁ(OPENE OAK
份不涉到造;3外供除)。
OKIRAN #TES A✯
((BA) (RCE)
,你不能实生形成控作器;今只有擁有大量
7) a
(L)有限公司忠區篩乃指(11时限收官十人;回資本
包裝)
TATAVEN QUER#Z00
Heat produced per min,
H.T. Battery
- ( 12 )1⁄2 x 1 x 60 x
82.3 calories
amp.
inside the cel
12 cal.
(M)稅納(Line持從外國入口貨徵!
KZKA ORDE OKREAD Ryo
(M)
(NO RECOLES ON
(N)
(O) ONE-ZHKË (OIAZ, ANTONIKA GALESETT DAM
(iii) ka the negative charges on the belt approach
the sharp point B which is attached to the sphere, they repel electrons away from the tip B towards the aphere and B is left with✨ a positiva charge. The strong electric field Bet up between B and the belt causes electrons to flow from the balt to the point B, thus neutralizing the positive charge on B. (iv) The above process is continuous, the aphare stores up electrical energy, storing up electrons, on the outside of the aphere, by means of mechanical work done by the motor. Charges reside on the outside of a hollow conductor. No charges are found inside it.
(b) Compare the EMS of a Janioll Call with another
When the resistors are in parallel
External resis
20
Current in the direul
ohm
(P)超過(二千入;每三十,3叫十人合股評選 艺品生意,作法,更宏愿以只有限公司。 (Q)保舍不得用二满(每千四號,十五號下四
(B)工業系列定(十四歲;三十六版;3十七機
中)以下安年,其工作時將包日不怎超治不小時。 (5)為龍出口中,本地工業製品約佔百分之(国八
十五;海九十四九十五)。
(R)-
C5)
(T) TOT
DE
(T)
(二)試將有經濟及公眾不滿之正確生發於右邊之適當選內。
CA)負賨音中常放映影片之政府機篇:
(A)
(B)
amp.
(B)
【 Heat produced in the cali
1 x 60x
515 calories.
(B)
(C)新界民政署分叫世施飲,就回度爲:
10.(a)
(c).
THE MOVING COLL GALVANORITER
(D)
Horseshoe
(D.)
Scale
Magnet
CE)
Pointer
deflection
core
The circuit is connected up as shown in Figure above. E. is the accumulator which serves to establish a pid, along the potentiometer wire AB. E. and E. represents in turn the Daniell cell and the cell to be compared. It is important to connect all the positive terminals of the cells to A of the potentiometer wire. When the driving circuit is closed, the tapper C starts the tapping off first near end A of the potentiometer wire, and then near B. The galvanometer should show opposite. deflections, If not the circuit should be checked and rearranged. Tapper U should tap along the wire to obtain a balance at C for the Daniell cell and C' for the other cell, The lengths and for the corresponding balance points C and C' are measured.
The theory and calculation of the comparison.
-arat
The potential difference between the points and C of the potentiometer wire is
Hene
A-C
I resistance of AC
Il
here is the specific resistance of the
wire is the length of AC
A is the area of cross-section of
the wife
(12)l
Since I, JA are
At balance
constant along the wire.
amf.of the Daniell call
positive
terminal
negative
terminal
The essential parts are a permanent horseshoe magnet; a movable coil suspended on jeweled bearings between the magnet poles, and two springs to restrain the coil movement. The springs also serve to carry current into and away from the coil. Attached to the coil is a
pointer which moves over an indicating scale. Whan a current passes through the coal, it acquiren polarity; its north pole turna toward the south pole of the magnet, and its south pole toward the north of the magnet. The amount of rotation of the coil depends upon the strength of the magnetic field produced by the
coll, and hence depends upon the intensity of the current flowing in the coil,
b) A high sensitivity is obtained by having (1) a large number of turne in the opil;
a very thin suspension with a small torsional controls
(3) a special alloy permanent magnet which
gives a very powerful magnetic field.
c)(1) Maximum current the galvanometer can resis
12.x 10 amp.
Resistance of the galvanoMGLOS
onme'.
It can tolerate a p.d. of 12 x 5 x 10′′:
volta that is. 0.06 volti
12 MA
R
(G)
(G)
(G)
•(G)
(H)
(H)
CH)
(H)
(1)股退之費與普通商品之發有何分
(一)香港資有有點?况下,香港出奇,並注重何方面之推行之? (=)@HAYRAT FINKELRYS JEUNG WAN INC (三)人口統計有信用您?就此城桃|||跟汁藏。 (*)***EKTAMATAY ZAVEZZE, 'KILEGNI (五)聯合國成立之宗旨為何?簡述其主要機作之工作及興之帶
Ans. A resistance of 995 ohms is connected
to the galvanometer, converting it into a voltmeter.
12). When converting the galvanometer into an ammeter of measuring current to 12 amp., would be necessary to use a shunt which passed (12 - 12 x 10-3) amp. while the meter carries only 0.012 amp.
#ZA
D-DIZA
Let R be the shunt used
(0,012 x 5 -11.988R
0.06
emf. of the other call
p.d.
各
Elz
sensitive centre-zero galvanometer and safety resistor is inserted to the circuit to guard the galvanometer against heavy currents. The safety resistor of 2000 ohne or more is
11.988
10.6 v.
-7.2.1.
In order to converted it into a voltmeter with a full scale deflection of 12 volte, a multiplier is used,
This multiplier, a seried connected/ resistance has to stand a p.d. of (12 -0,06) volts. Its resistance thereforei
R
-12-0,06
12 x 10 995 ohm's
* 24 x 103
12
0,00498 ohm
Ans. A shunt of 0.00498 ohm is used.
(d) A voltmeter measures the potential difference between two points in a circuit. Generally, a voltmeter is of the moving coil type. It is essentially a galvanometer with a high- resistance coil (multiplier) in series with it. The high resistance limits the current through the meter. When the meter is connected to the Dell, it measures the approximate value of its enf. only. For no matter how large the multiplier 13, there is still a current passing.
So there is a IR loss. The emf, thús measured 18 not the actual one.
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