A student is investigating the behaviour of a capacitor-resistor circuit as shown in Fig. 1.1. [Figure 1.1] A neon lamp flashes on and off when it is connected across the capacitor with a potential difference V_F across the lamp of approximately 90 V. The student has a number of unmarked resistors. It is suggested that the period T of the flashes of the lamp is related to the resistance R of the resistor by the expression T = RCK where C is the capacitance of the capacitor and K is a constant. The constant K is given by K = ln ( (V_I - V_F) / V_L ) where V_I is the potential difference across the input, V_F is the potential difference required to make the lamp flash and V_L is a constant. Design a laboratory experiment to test the relationship between T and R. Explain how your results could be used to determine a value for K and V_L. You should draw a diagram, on page 3, showing the arrangement of your equipment. In your account you should pay particular attention to: • the procedure to be followed • the measurements to be taken • the control of variables • the analysis of the data • any safety precautions to be taken.

1. (a)A student is investigating the behaviour of a capacitor-resistor circuit as shown in Fig. 1.1. [Figure 1.1] A neon lamp flashes on and off when it is connected across the capacitor with a potential difference V_F across the lamp of approximately 90 V. The student has a number of unmarked resistors. It is suggested that the period T of the flashes of the lamp is related to the resistance R of the resistor by the expression T = RCK where C is the capacitance of the capacitor and K is a constant. The constant K is given by K = ln ( (V_I - V_F) / V_L ) where V_I is the potential difference across the input, V_F is the potential difference required to make the lamp flash and V_L is a constant. Design a laboratory experiment to test the relationship between T and R. Explain how your results could be used to determine a value for K and V_L. You should draw a diagram, on page 3, showing the arrangement of your equipment. In your account you should pay particular attention to: • the procedure to be followed • the measurements to be taken • the control of variables • the analysis of the data • any safety precautions to be taken.[15]

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