Cambridge IGCSE Physics - 0625 - Core Paper 3 2014 Summer Zone 1

A gardener studies the growth of one of his plants. At the same time each day, he measures the height $h$ of the top of the plant from the ground, as shown in Fig. 1.1.

The table of his results is shown below.
[Table_1]
(a) From the values in the table, deduce the average speed of growth of the plant during the 7 days. Work in days and cm.
average speed = ..................................... cm/day [4]
(b) (i) Complete Fig. 1.2 by plotting the last three values of height $h$ against time. Do not draw a line through the points.
[2]
(ii) Describe how the graph shows that the speed of growth of the plant is not constant. .......................................................................................................................................................... .......................................................................................................................................................... [1]

Fig. 2.1 shows a spring before and after a load is added.
!
(a) What is meant by the extension of the spring?
..................................................................................................................
..................................................................................................................[1]
(b) When the graph of extension against load is drawn for the spring, the result is the line shown in Fig. 2.2.
!
(i) The unstretched length of the spring is 9.0 cm.
1. Calculate the total length of the spring when a 5.0 N load is hanging from the spring.
length = ................................................. cm [2]
2. Find the extension that will be caused by a load of 2.0 N.
extension = ........................................... cm [1]
(ii) Calculate the mass of a load of weight 2.0 N.
mass = ................................................[2]

The apparatus in Fig. 3.1 is being used to view the movement of some smoke particles trapped in a box.
[Image_1: Fig. 3.1]
(a) Describe what is seen when the smoke is viewed through the microscope.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................[2]
(b) In the space below, sketch how one smoke particle might move during a short interval of time.
[2]
(c) What causes the smoke particles to move?
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................[2]
(d) What name is used for this motion of the smoke particles? Complete the sentence.
The motion of the smoke particles is known as .................................................. motion. [1]

A young boy, skating on a frozen pond, has fallen through some thin ice about 10 m from the shore of the pond. Fig. 4.1 shows the situation. A man, standing near the pond, hears the boy’s shouts for help. The man weighs more than the boy.
(a) Why would it be unsafe for the man to walk on the ice to rescue the boy? ........................................................................................................................................................................................... ........................................................................................................................................................................................... [1]
(b) Suggest and explain what the man could do to cross the ice to reach the boy safely. ........................................................................................................................................................................................... ........................................................................................................................................................................................... ........................................................................................................................................................................................... ........................................................................................................................................................................................... [4]

The thermometer in Fig. 5.1 is recording the temperature of the laboratory.
(a) The bulb of the thermometer is placed in pure, boiling water at standard atmospheric pressure.
State the temperature increase.
temperature increase = ..................................................... °C [1]
(b) During the day, the temperature in the laboratory rises. In the late afternoon a thermometer attached to the ceiling records a higher temperature than a thermometer placed close to the ground.
Explain why this happens.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................ [3]
(c) At night, the temperature in the laboratory falls.
Describe what can be seen happening to the liquid in a thermometer as the temperature falls, and explain why this happens.
........................................................................................................................
........................................................................................................................
........................................................................................................................ [2]
(d) On Fig. 5.1, draw an arrow to show where the end of the liquid thread might be seen when the temperature being measured is −15°C. [1]

(a) A periscope is an optical instrument containing two mirrors in a long tube.

Fig. 6.1 shows the path of a ray of light through a periscope, without the tube.



(i) On Fig. 6.1,
1. use the letter $i$ to indicate clearly the angle of incidence of the ray striking mirror A,
2. use the letter $r$ to indicate clearly the angle of reflection of the ray leaving mirror A. [1]

(ii) Write down the equation that links $i$ and $r$.
................................................................................................................................... [1]

(iii) Suggest a use for the periscope.
................................................................................................................................... [1]

(iv) State what happens if mirror B is rotated through a small angle.
................................................................................................................................... [1]

(b) Fig. 6.2 shows a converging lens. The lens has one principal focus at $F_1$ and the other principal focus at $F_2$.



Use your ruler to help you answer this question.

(i) On Fig. 6.2, clearly mark two distances that are each the focal length of the lens. [1]

(ii) On Fig. 6.2, draw a ray on the left side of the lens, which strikes the lens, above and parallel to the principal axis. Label this ray: ray 1.
Continue this ray to show its path through the lens and at least 6 cm to the right of the lens. [2]

(iii) On Fig. 6.2, draw a ray that emerges from the lens, below and parallel to the principal axis. Label this ray: ray 2.
Show clearly the path of this ray before it reached the lens. [1]

In Fig. 7.1, XY is a copper rod placed between the N and S poles of a magnet.

!

XY is connected to the terminals A and B of a sensitive, centre-zero instrument that measures current.

(a) State the name of this instrument. ......................................................[1]

(b) When there is no current, the pointer on the instrument points half-way between A and B. State what, if anything, is seen happening to the pointer when XY is

(i) held stationary, ............................................................[1]

(ii) moved horizontally at a steady speed towards the N pole, ............................................................[1]

(iii) moved horizontally at a steady speed towards the S pole, ............................................................[1]

(iv) moved repeatedly up and down at right angles to the magnetic field. ............................................................[2]

(c) Suggest one electrical device that makes use of the effect demonstrated in (b). ............................................................[1]

A student connects the circuit shown in Fig. 8.1.

When operating normally, the lamp has a resistance of 10Ω.
(a) (i) State the current in the lamp when both $S_1$ and $S_2$ are open.................................................................................................................................[1]
(ii) The student closes switch $S_1$.
Calculate the current in the lamp, stating the unit of your answer.

current = .................................................... [4]
(iii) The student now closes $S_2$ as well as $S_1$.
State the current in the lamp with both switches closed.................................................................................................................................[1]
(b) The student decides that she would like to be able to vary the brightness of the lamp.
(i) Name an electrical component that she could add to the circuit to do this....................................................................................................[1]
(ii) In the space below, redraw the circuit of Fig. 8.1, including the component for varying the lamp brightness.
[2]

(a) Describe how the N pole of a bar magnet can be identified.
........................................................................................................................................................................
........................................................................................................................................................................
........................................................................................................................................................................[2]

(b) Use words from the following list to answer the three questions below.

A transformer is a device for changing voltages.
Fig. 10.1 shows a transformer that has a primary coil with 1000 turns and a secondary coil with 50 turns.



Fig. 10.1
(a) State the material from which the core of the transformer is made.
..............................................................................................................................................[1]

(b) The primary coil is connected to a 240V alternating current supply.
Calculate the voltage across the secondary coil.

secondary coil voltage = ....................................................... V [3]

Polonium-210 ($^{210}_{84} \text{Po}$) is radioactive.
(a) Name three types of emission from radioactive sources.
1. ..................................................................................................................
2. ..................................................................................................................
3. .................................................................................................................. [2]
(b) State which of these radiations
(i) carries a negative charge, ...............................................................................
(ii) is most easily absorbed, ................................................................................
(iii) is the emitted particle in the decay
$^{210}_{84} \text{Po} \longrightarrow ^{206}_{82} \text{Pb} +$ emitted particle. ..................................... [3]
(c) Polonium-210 has a half-life of 138 days.
A sample containing $8 \times 10^{10}$ atoms of polonium-210 decays for 276 days.
(i) How many half-lives elapse in this time? ..........................................................
(ii) How many atoms decay in this time?
number that decay = ..................................................
(iii) How many particles are emitted from the polonium-210 during this time?
number emitted = .................................................. [4]

One nuclide of chlorine has 35 nucleons and the other nuclide of chlorine has 37 nucleons. The proton number of chlorine is 17.
(a) How many protons are there in a neutral atom of chlorine-35? ..........................................................
(b) How many neutrons are there in a neutral atom of chlorine-37? ..........................................................
(c) How many electrons are there in a neutral atom of chlorine-37? ..........................................................