4 13670.13 RRR Question 2 Requirements • 1000 F capacitor • 22 k resistor • Masking tape • Variable Power Supply to supply at least 5V D.C. • Resistance substitution box with 10 k, 22 k, 47 k, 100 k and 220 k values. E.g. Philip Harris B8H27234 OR Resistance selector box with 6.8 k10k33k47kand100kvalues, e.g. SLS Lascells PY3110 • Digital Voltmeter 0–20 V to 0.01 V DC • Connecting leads (approx. 9) • Stopclock to 0.01 s • Component holders × 2 • Sticky labels • Two way switch Preparation Wrap both the capacitor and the 22 k resistor in masking tape so that the values of the capacitance and resistance cannot be seen. Place the capacitor and resistor into the component holders and label them ‘capacitor’ and ‘RF’. Label the resistance substitution box as ‘RV’. Set up the circuit as shown in Fig 2.1. Two-way switch Fig 2.1 5 13670.13 RRR Place a label on the two-way switch with the words ‘charge’ and ‘discharge’ on it to indicate the correct positions. Turn the two way switch to the charged position and turn the dial on the variable power supply until the voltmeter reads approximately 5V. Place a label stating ‘do not touch’ onto the dial of the power supply. Turn the dial on the resistance substitution box to 10 k. Action at Changeover Ensure the circuit is as shown in Fig 2.1. Place the two-way switch into the charged position and check the voltmeter reads approximately 5V. Turn the dial on the resistance substitution box to 10 k. Reset the stopclock to zero.