異二第六第
日六廿月四年申戊潛夏
1408.英文中學會考試題預習專欄
TIO
WAH KIU YAT PC #
三期星
日二廿月五年八六九一层公年七十五委民军
For the closed pipe
wavelength of the fundamental - al
(b)(1) Chur's Law
2
800 cm.
The current passing through-a wire st
+
constant temperature is proportional to the
potential difference betimen its ends,
wavelength of the 1st overtone
#
3
(11) Measurement of resistance by anmater voltastar method,
-
4 x 200
*ZIL)
(1) a very high resistance
1
物理科 (三十)
·隆永爟・!
'Physics (30)
8. (a) The "amplitude of a wave motion is the
magnitude of the maximum displacement of the} vibrating particle from its mean position.
The number of cycles executed in a unit) is known as the frequency of the wave
time motion.
A wavelength is the distance between two successive points which are in the same phase and in the same direction of the wave motion,
a
amplitude of ware.
wavelength)
Frequency of the fundamental *
34000 800
42.5 0.
..
34000 x 3
Frequency of 1st overtone
=
- 127.5 c.p.s.*
PRAPË JEMI SE SA SE DA
(d) The interval between each pair of the adjacent
strings E, A, D, G is a fifth, giving a frequency of 3/2.
Since.
I =
1
z l
F
where is the natural frequency of the string
Lis the length of the string
T is the tension
M is the mass per unitlength of the
string.
Ifland T are constant, the ratio of the frequencies of adjacent strings will be
Valtmeter is connected across R and the aumater. The ammeter reads the actual current passing through E. The voltmeter gives, the p.d, across Rand A. As resistance of the ammeter is very small as compare with R, the p.d, acrose A is negligible.
(2) a very low resistance
书
to To Find the velocity of sound in air:
A tuning fork of known frequency, f. la sounded and held over a column of air. This column is open at the top, closed at the bottom) and is adjustable in length. As the water in the resonance tube is moved up and down, by the raising or lowering of the reservoir, it is noticed that sound is heard more intense at certain definite lengths of the air column. The shortest resonant length has the greatest intensity andzis found to be tλ in length. The next is
since
M
A
MoC Area
(rad)
oc (diameter
The ammeter A reads the current passing through R plus that through the voltmeter. The resistance of the voltmeter is much larger than that of R. Therefore, the current passing through H is negligibly small.
(*) Total internal resistance of cells - 3 ohms
Equivalent resistance of the parallel resistors'
600 50
*
20 x 30 20. 30
•
12 ohms,
Total external resistance = 10 + 12 + 5
- 27 ohms.
Total resistance of the circuit - 27 + 3
30 ohms,
•
"Ins ́anti-node"at"the top does not coincias ↑
exactly with the top of the tube but slightly -about it by an amount called end-correction C
Thus, if the first resonant
Length
CE,
‚and, the 2nd resonant langth"= £2_am..
then,
4
དྭེ -ཙམཾ, –དྷམཾ,
at Clay - lid
0.
- 0.6'..
Similarly,
** 0.9 to the
* 0.6)
2
and,
3 x 2
(1) Current through the lamp -
- 0,2 &mpɔ.
30
>
·
x 0.9
G
2
1.35. the
The diangler ef, the A, D. and G strings-åre 0.9 m. m, and 1.35 m.m. respectively,
Current in the 20-oha resistor - - x 0,2 amp,
5 = 0.13 amp. (11) Beat produced in the 20-ohm resistor in
an hour (0.12) x 20 x 3600 joules
- 247 calories
36 1010
Tiii) Mass of copper deposited
- 0.00033 * 0.2 × 30 × 60--- -0.1188 g
DE 20
electron
floud
current.
Copper
blat.
9. (a) Action of simple
Zine
plate
ONG KONG PUBLIC
The velocity of sound în air in," therefore. de farmined.
open pipa.
close pipe
In each diagram the distribution of nodes and antinodes is shown; the fundamental on the left and the first overtone on the right. For the oven oipe:
wavelength_of the fundamental -
ת
400 CEL,
wavelength of lat overtone
*". Frequency of the fundamental ➡ 我
34000
- 200 cm3
V
400
• 85 c.p.7.
31.000
200
Low 375.3. P.B
A simple cell composes of a plate b copper and a plate of sino dipping into dilute. sulphuria said.
When the plates are joined by a wire the - sine begins to dissolve in the add.
(a) 1) Whine a p.d. of 220 volts is applied an
the lamp it works with a power of 200 watts.
11) Since Power, P =
(p.d.)2
KARIES
Dilute sulphuric, acid sölution ionises all (H*) and{50~~) lons, Ae.gine atoms dissolve they go into the solution as Za** sach leaves. two electrons behind 'the plate making it negative,
Hydrogen ions (H') migrate to the copper plate where they receive electrons becoming nential and are liberated to form gas bubbles,
By losing electrons, the copper plate becomes positively charged, and this enables electrons to flow from the negative zine plate to the positive copper plate.
(1) Polari sa ti og
The formation of a layer of hydrogen “ bubbles on the copper plate will:.
(1) set up a "back's,maí." An opposition to the
e.m.f. of the call.
(2) suffocate the Tation due to the insulation
of the surrounding layer of hydrogen bubbles.
This is known as Polarization.
(11) Local action
The impurities of commercial sino, such as iron or carbon, set up tiny sells at the zino surface, Bubbles of hydrogen are given off. This sarvas na useful purpose but only vaste the sins and is known as local action.
(111) The potential difference of the plates
less than 1.volt, esta- up an e.k.f. but it
polarisation.
the
resistance
2202
. Resistance R =
200
242 ohms
ME TE TO
111) If two of these lampa are în series, wachi
lamp is under a p.d. of 110 volts.
A
PS
(where R is constant)
R
Therefore, power of each lamp is four times) 1985,
200
P.
• 50 watts
Energy consumed in 24 hours ·
2 x 50 x 24.
·
KW--FT"=
1000
- 2.4 kWykr.
Fest in runing the lamps for 24 nr.-
(2.4 x 0,3) 12.22
(b) Lat, the e.m.f. be E volts and the internal regiatanos be rohms and the external resistances for the two different circuits are R. and R2 chat respectively.
Since the terminal p.d. is across the external resistance,
Therefore, R, x1 - 28.5
A x 2 - 27
The .f, is the product of current and the total resistance (both external and internal, in the circuit.
E
(8, + r) x 1
E = (R2 + r) x 2
^, • r • (R5+ r) 2
28.5 + r - 2(13.5 + r)
pm-1,5
Therefore E = 28.5 +2.5
- 30
¿Ans, The internal resistance of the battery 18,
(REGARROBAR 2