Question

(a) Fig. 12.1 shows an electric heater used in a classroom in a school.

The air around the heater is warmed.
(i) On Fig. 12.1 draw three more arrows to show how the warmed air moves around the classroom.
One arrow has been drawn for you. 
(ii) State the name of the method of thermal energy transfer you have drawn in (a)(i).

(b) The teacher in the classroom measures the temperature in the room with a thermometer.
Fig. 12.2 shows the thermometer.

(i) State the name of the temperature scale used on the thermometer.
(ii) State the name of a liquid that is used in thermometers.
(iii) State the physical property of the liquid that varies with temperature.

(c) (i) In the school an electric bell rings to show that the lesson has ended.
The bell makes sound waves that travel through the air.
Sound waves cannot travel through a vacuum.
Explain why sound cannot travel through a vacuum.
(ii) Inside the electric bell there is a solenoid.
The solenoid coil is shown in Fig. 12.3.

On Fig. 12.3, draw the pattern of the magnetic field that is produced when an electric current passes through the solenoid as shown. 

▶️Answer/Explanation

Ans :  12(a)(i) arrow
               across the top
               then dropping down
               then left to right along floor
               1 mark for any one correct arrow ;
               1 mark for all three arrows correct ;

12(a)(ii) convection ; 
12(b)(i) celsius ; 
12(b)(ii) alcohol or mercury ; 
12(b)(iii) volume / density ; 
12(c)(i) There is no medium (for the propagation of the sound wave) ; 
12(c)(ii) at least two lines going all the way through coil ;
                line curving upwards and line curving downwards ;