物理 2009 年 DSE、CE 選擇題（第 2 頁）

11.

Temperature (degrees C) against time (s): rises from 30 to 60 degrees C in 60 s, then stays at 60 degrees C

When a certain mass of a solid substance is heated by a heater of constant power, the variation of its temperature with time is shown in the figure above. If a greater mass of the same substance is heated by the same heater, which of the following graphs best represents how its temperature varies with time ? (Assume no heat lost to the surroundings.)

12.

In an experiment, a kilowatt-hour meter is used to measure the energy supplied to an immersion heater. An electronic balance is used to measure the change of the mass. The data obtained is used to estimate the specific latent heat of vaporization of water ( $l$ ).

Polystyrene cup of water with immersion heater connected to a kilowatt-hour meter, standing on an electronic balance

If the following experimental error arises : (I) Water splashes out of the polystyrene cup as the boiling is too vigorous. (II) Water vapour condenses on the upper part of the heater and drips back into the polystyrene cup. How would the calculated value of $l$ be affected ?

	(I)	(II)
	increases	decreases
	increases	increases
	decreases	decreases
	decreases	increases

13.

A student puts a lens at a certain distance above a paper with the word "TEST" written on it as shown in the figure. What is the lens ? If the student moves the lens further away from the paper, what will be the change in the size of the image ?

The word TEST magnified by a circular lens held over a ruled paper

	lens	change in size of the image
	convex	increases
	convex	decreases
	concave	increases
	concave	decreases

14.

Water wave travelling towards a floating cork, with 0.4 m and 0.6 m distances marked

A cork is floating on a calm water surface as shown in the above figure. At time $t=0$ , a water wave is travelling towards the cork with a speed of $0.2\ \mathrm{m\,s^{-1}}$ . When will the cork rise to its highest position for the first time ?

15.

Two coloured lights X and Y travelling from vacuum into glass along the same path in glass

Two coloured lights, $X$ and $Y$ , travel from vacuum to glass. They undergo refraction and travel along the same path in glass. Which of the following descriptions about the two coloured lights is correct ?

16.

Which of the following graphs showing the relationship among velocity ( $v$ ), frequency ( $f$ ) and wavelength ( $\lambda$ ) of electromagnetic waves in vacuum is/are correct ?

Three graphs: (1) v against f horizontal line; (2) f against wavelength straight line rising; (3) v against wavelength horizontal line

17.

Light bulb X and convex lens L with the light converging beyond the lens

In the above figure, $X$ is a light bulb and $L$ is a convex lens. Which of the following ways can be used to produce a parallel beam of light rays ?

(1)Moving

L

closer to

X

.

(2)Replacing

L

with another convex lens of longer focal length

(3)Replacing

L

with another concave lens of shorter focal length

18.

Two identical bulbs, $X$ and $Y$ , are connected in parallel to the mains. The current passing through $X$ is $0.4$ A. What is the energy consumed by the two bulbs in $5$ hours ?

Two bulbs X and Y connected in parallel to a 220 V supply

19.

Two identical resistors are connected in series in the circuit shown. What are the readings of the voltmeter when $S$ is open and when $S$ is closed respectively ?

12 V battery with two resistors in series, switch S, and a voltmeter across the second resistor and the switch

	$S$ is open	$S$ is closed
	zero	$6$ V
	zero	$12$ V
	$12$ V	$6$ V
	$12$ V	$12$ V

20.

The power ratings and resistances of two light bulbs are " $24$ W, $6\ \Omega$ " and " $9$ W, $4\ \Omega$ " respectively. If these two light bulbs are connected in parallel to a power supply, what is the maximum current drawn from the power supply so that both light bulbs are working within the rated power ?