CIE iGCSE Co-Ordinated Science P4.2.1 Electrical charge Exam Style Questions Paper 4
Question
A student investigates the use of cotton wool to insulate a beaker of hot water at 90°C.
(a) The student uses a digital thermometer to measure the temperature of the water in the beaker as it cools.
The student repeats the experiment using different thicknesses of cotton wool.
Fig. 9.1 shows a graph of the results.
(i) Predict the temperature after 5.0 minutes of a beaker of water which is insulated with 2.0cm of insulation.
Use the results shown in Fig. 9.1 to explain your answer.
temperature …………………………………. °C
explanation …………………………………………………………………………………………………………
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(ii) Complete the sentences about the digital thermometer.
The digital thermometer contains two wires made of different metals.
The wires are joined together at each end to form two junctions.
This arrangement is known as a …………………………………………. .
(b) The student uses an electric kettle to heat the water for the investigation.
The electric kettle has a power rating of 1800W when a potential difference of 240V is applied.
Calculate the resistance of the kettle.
resistance = ……………………………………………… Ω
(c) Plastic is an electrical insulator.
Fig. 9.2 shows two lightweight, plastic sheets suspended by insulating threads.
Each plastic sheet is positively charged.
(i) Explain what is observed when the two plastic sheets are moved close to each other.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(ii) Describe how a plastic sheet can become positively charged.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 9(a)(i) any temperature in the inclusive range 36–50 (°C) ;
2.0cm reduces the rate of conduction (to the surroundings) more than 1.0cm but less than 3.0cm / OWTTE ;
9(a)(ii) thermocouple ;
9(b) evidence of (I =) P ÷ V or 1800 ÷ 240 ;
(I =) 7.5 (A) ;
evidence of R = V ÷ I or 240 ÷ 7.5 ;
(R =) 32 (Ω) ;
9(c)(i) move away from each other ;
like charges repel ;
9(c)(ii) friction (with another surface) ;
transfer of electrons ;
(particles move) from the plastic / to the surface it is rubbing against ;