物理 1997 年 DSE、CE 選擇題（第 2 頁）

11.

A fixed mass of gas at $120^\circ$ C is heated at constant volume so that its pressure is tripled. Find the new temperature of the gas.

12.

Which of the following graphs correctly shows the relation between the pressure $P$ and volume $V$ of a fixed mass of gas at constant temperature ?

Four graphs: A P against 1/V curve; B 1/P against 1/V straight line; C P against 1/V straight line through the origin with dashed extension; D P against V straight line

13.

The apparatus is used to find the specific heat capacity of a liquid. Which of the following can improve the accuracy of the experiment ?

(1)Take the final temperature of the liquid immediately after switching off the power supply.

(2)Cover the cup with a lid.

(3)Stir the liquid throughout the experiment.

Cup of liquid with thermometer and immersion heater connected to a power supply

14.

An heater with a power of $100$ W is used to heat $0.3$ kg of a liquid which has a specific heat capacity of $2000\ \mathrm{J\,kg^{-1}\,{}^\circ C^{-1}}$ . If the initial temperature of the liquid is $23^\circ\mathrm{C}$ , find its temperature after $2$ minutes. Assume all the energy given out by the heater is absorbed by the liquid.

15.

Mechanical model of a gas: a cylinder with ball bearings under a disc, on a vibrating platform driven by a motor

The diagram shows a mechanical model of a gas. The weight of the disc and the power of the motor can give a measure of two different properties of the gas. What are these two properties ?

	Weight of the disc	Power of the motor
	Pressure	Volume
	Pressure	Temperature
	Volume	Temperature
	Temperature	Pressure

16.

Which of the following statements concerning microwaves and ultrasonic waves is/are correct ?

(1)Microwaves are electromagnetic waves while ultrasonic waves are not.

(2)Microwaves and ultrasonic waves travel with the same speed in air.

(3)Microwaves can be diffracted while ultrasonic waves cannot.

17.

Questions 23 and 24 : A vibrator generates a stationary wave on a string. The diagram below shows the string at a certain instant.

Stationary wave on a string between a vibrator and a fixed end, with particles X and Y marked

Which of the following statements is incorrect ?

18.

Questions 23 and 24 : A vibrator generates a stationary wave on a string. The diagram below shows the string at a certain instant.

The vibrating string also sets the neighbouring air into vibration. Which of the following statements about the waves on the string and those in air must be correct ?

19.

Vibrator producing plane waves in a ripple tank towards a slit in a barrier

A vibrator generates continuous plane waves in a ripple tank. The waves undergo diffraction when they pass through a slit. Which of the following can increase the degree of diffraction of the waves ?

(1)Increasing the width of the slit

(2)Placing the vibrator closer to the slit

(3)Increasing the wavelength of the water waves

20.

Which of the following is an application of ultra-violet radiation ?