物理 2005 年 DSE、CE 選擇題（第 4 頁）

31.

Questions 34 and 35 : The displacement-distance graphs of the particles along a travelling wave at time $t=0$ and $t=0.2$ s are shown below.

Two displacement-distance graphs on grids (2 cm squares), at t = 0 and t = 0.2 s

Which of the following statements about the wave are correct ?

(1)Its amplitude is

6

cm.

(2)Its wavelength is

8

cm.

(3)Its frequency is

5

Hz.

32.

Questions 34 and 35 : The displacement-distance graphs of the particles along a travelling wave at time $t=0$ and $t=0.2$ s are shown below.

What is the speed of the wave ?

33.

An interference pattern is formed by two coherent point sources of water waves. Which of the following variations can change the positions of constructive interference ?

(1)changing the amplitude of the waves

(2)changing the wavelength of the waves

(3)changing the separation between the point sources

34.

Which of the following is a unit of sound intensity level ?

35.

Two musical notes are produced by two different kinds of musical instruments. The two notes have the same pitch but different loudness. Which of the following combinations of notes satisfies the above description ? Note : The settings of the CRO for displaying the notes are identical.

Four pairs of CRO traces labelled A to D

36.

Pictorial circuit with battery box, switch, ammeter, voltmeter, rheostat and resistor R

A student wants to measure the resistance of a resistor $R$ and sets up a circuit as shown above. Which of the following describe(s) the mistake(s) made by the student in setting up the circuit ?

(1)The polarity of the ammeter is reversed.

(2)The polarity of the voltmeter is reversed.

(3)The voltmeter is connected across both

R

and the rheostat.

37.

Questions 84 and 85 :

Circuit with cell, ammeter, resistor and thermistor in series and a voltmeter across the thermistor

A teacher sets up the circuit as shown in the above Figure and provides the following information to her students.

Information scroll: thermistors are devices whose resistance varies with temperature; graph of resistance against temperature falling steeply then flattening

Which of the following shows the variation of the ammeter reading $I$ with the temperature of the thermistor $\theta$ ?

38.

Questions 84 and 85 :

A teacher sets up the circuit as shown in the above Figure and provides the following information to her students.

Which of the following shows the variation of the voltmeter reading $V$ with the temperature of the thermistor $\theta$ ?

39.

Which of the following statements about long distance power transmission at high alternating voltages are correct ?

(1)Alternating voltages can be stepped up or down efficiently by transformers.

(2)For a given transmitted power, the current will be reduced if a high voltage is adopted.

(3)The power loss in the transmission cables will be reduced if a high voltage is adopted.