Question

Fig. 9.1 shows a washing machine.

(a) (i) The washing machine uses:
• a heater to heat the water
• a motor to pump the hot water through the machine.
The motor and the heater are connected in a parallel circuit.
The motor and the heater are each operated by separate switches.
The circuit symbol for a heater is       

The circuit symbol for a motor is           
Fig. 9.2 shows an incomplete circuit diagram for the washing machine.
Complete the circuit diagram on Fig. 9.2.

(ii) The resistance of the heater is 20 Ω.
The resistance of the motor is 80 Ω.
Identify from the list the most likely value for the combined resistance of the heater and
motor connected in parallel.
Explain your answer.
          16 Ω          20 Ω        50 Ω          80 Ω         100 Ω
combined resistance = …………………………. Ω
explanation …………………………………………………………………………………………………………

(iii) The current in the wires of the electrical circuit is a flow of charged particles.
State the name of the particles that flow in the wires of the electrical circuit.
(iv) The current-carrying coil in the motor experiences a turning effect.
This turning effect can be increased by increasing the number of turns on the coil.
State two other ways to increase this turning effect.
1 …………………………………………………………………………
2 …………………………………………………………………………
(b) Inside the washing machine, some of the water evaporates.
During evaporation, water changes state from a liquid to a gas.
(i) Complete the diagrams in Fig. 9.3 to show the arrangement and separation of molecules
in a liquid and in a gas.

(ii) During evaporation, the water does not boil.
State the boiling point of water.
                         …………………………………………….. °C

▶️Answer/Explanation

Ans : 9(a)(i) all symbols correct ;
heater and motor in parallel connection ;
switches correctly placed ;
9(a)(ii) 16 (Ω) ;
combined resistance in parallel is less than either individual resistance ;
9(a)(iii) electrons ; 
9(a)(iv) increase current ;
increase strength of magnetic field ;
9(b)(i) liquid – all molecules touching random arrangement ;
gas – molecules widely separated (no more than seven shown) and random arrangement ;
9(b)(ii) 100 (°C) ;