Discharging of a capacitor for AL CAIE Grade11 .pptx

2025 CAIE AL

1. Discharg ing of a capacitor

2. CONTENTS 目录 01 Review 03 Determine the capacitance 04 Discharging a capacitor 05 Past paper questions 06 Assignment 02 Safety Precautions

3. Equation about discharge of capacitor PART 01

4. 1. E quation X = X e –(t / RC) X could be: Current/ I Charge/Q Potential difference/V

5. 2. time constant τ = RC R for Resistance in O hm C for Capacitance in Farad

6. Safety precautions PART 02

7. Safety precautions When handling capacitors or conducting discharging procedures, use the "one hand" rule. Keep one hand behind your back or in your pocket to minimize the risk of completing a circuit through your chest. 05 Always verify that the voltage across the capacitor is discharged to a safe level using a voltmeter or multimeter before touching any part of the circuit. 03 Use a discharging tool (e.g., a resistor with appropriate resistance) to safely discharge the capacitor. Connect one end of the discharging tool to the terminal of the capacitor and the other end to the ground. 04 Wear appropriate personal protective equipment, including safety goggles , lab coat and insulating gloves 01 Before working on a circuit with capacitors, make sure the power source is disconnected, and the circuit is de-energized 02

8. Capacitor construction and capacitance measurement PART 0 3

9. apparatus should be used: multimeter , handmade capacitors C apacitor construction and capacitance measurement

10. Present the method for constructing a capacitor with maximum capacitance. Presentation Group 1 Group 2 Group 3 Group 4 Group 5 circuit 陈宇莹 阮之翰 高琬瑜 成怀瑾 崔梓墨 graphing 何延鼎 唐雅倩 戴玮 袁可人 熊益 speaker 柏熙 黄语桐 温志锐 周商羽 张语嘉 leader 黄博森 姚安北 何旭贤 王文熙 郭榕华

11. Discharging a capacitor PART 0 4

12. Apparatus Apparatus: a capacitor, a resistor, and a voltage source. 01

13. Circuit Setup Connect the capacitor, resistor, and power source in a circuit. Ensure the connections are secure. 02

14. Charging 03 Prior to the activity, ensure that the capacitor is fully charged. You can do this by connecting it to the power source and allowing it to charge for a brief period.

15. Observation Observation: Once the capacitor is fully charged, disconnect it from the power source and begin the observation. Record the potential difference (voltage) across the capacitor at regular time intervals. 04

16. Data Analysis Plot the voltage against time on a graph to create a discharging curve. 05

17. Discussion Observe and discuss the exponential decay nature of the curve. 06

18. Past paper questions PART 0 5

19. Question from past paper A capacitor, a battery of electromotive force ( e.m.f. ) 12V, a resistor R and a two-way switch are connected in the circuit shown in Fig. 5.1. The switch is initially in position S. When the capacitor is fully charged, the switch is moved to position T so that the capacitor discharges. At time t after the switch is moved the charge on the capacitor is Q. The variation with t of ln(Q/ μC ) is shown in Fig. 5.2. Show that the capacitance of the capacitor is 1.5μF. Determine the resistance of R. Calculate the energy stored in the capacitor at time t = 0.

20. Assignment PART 0 6

21. Consider these questions: What would happen if we use low capacitance and low resistance to collect data? How would it affect the graph, and what about the data collection process? When charging the capacitor, is higher voltage always better, or is there an optimal maximum voltage? What could potentially happen to the capacitor if the voltage exceeds this limit? Can we use our homemade capacitor to create a camera flash? For the written work, please complete the questions in the capacitance workbook.