物理 1980 年 DSE、CE 選擇題（第 2 頁）

11.

$6\times10^{-3}$ m $^3$ of a gas is contained in a vessel at $91^\circ$ C and a pressure of $4\times10^5$ Pa. If the density of the gas at s.t.p. ( $0^\circ$ C and $10^5$ Pa) is $1.2$ kg m $^{-3}$ , what is the mass of the gas ?

12.

Cooling curves of liquids A and B: temperature against time, A with higher and longer plateau

Two liquids $A$ and $B$ are cooled in air. Their cooling curves are shown. If $A$ and $B$ have the same mass, which of the following statements is/are true ?

(1)

A

has a higher freezing point than

B

.

(2)

A

has a greater specific latent heat of fusion than

B

.

(3)Liquid

A

has a greater specific heat capacity than liquid

B

.

13.

When a mercury thermometer is immersed in melting ice and then in steam, the lengths of the mercury thread in the stem are respectively $2$ cm and $22$ cm. When the thermometer is put in a water bath, the length of the thread is $11$ cm. What is the temperature of the water bath ?

14.

Light ray passing through an air bubble in water, with four emergent rays P, Q, R and S

A light ray passes through a spherical air bubble in water. Which of the following represents the path of the emergent ray ?

15.

When light enters from one medium into another, which of the following will be changed ?

(1)The frequency of the light

(2)The wavelength of the light

(3)The velocity of the light

16.

A point light source is placed in a liquid. Rays from the source leave the liquid surface through a circular area of diameter $24$ cm. The refractive index of the liquid is $1.25$ . The depth of the source below the liquid surface is

17.

A convex lens is used to form an image of a bright object on a screen. The effect of covering the top half of the lens with a card is to

18.

A fixed object is placed in front of a plane mirror. If the mirror is moved $0.10$ m away from the fixed object, how far will the image move ?

19.

In the circuit shown, the battery has an e.m.f. of $6$ V with negligible internal resistance. Four resistors are connected to the battery as shown in the figure.

Two parallel branches (4 ohm and 8 ohm in series, 8 ohm and 4 ohm in series) joined at points P and Q, connected to a 6 V battery

What is the potential difference between points $P$ and $Q$ ?

20.

Circuit with D.C. source, fuse Y, fuse Z in series with a 21 ohm resistor, and fuse X in series with an 18 ohm resistor and switch K

In the circuit shown, $Y$ is a 5 A fuse, $Z$ and $X$ are 3 A fuses. When the switch $K$ is open the current passing through the $21\ \Omega$ resistor is $2.4$ A. When $K$ is closed, which of the fuses will be blown ?