Final answer:
To allow necessary measurements in ECG monitoring, the resistance and capacitance in the circuit should be decreased to reduce the RC time constant, which enables the detection of smaller time variations in voltage.
Step-by-step explanation:
When measuring voltage variations in an electrocardiogram (ECG), the RC time constant is a critical factor that determines the smallest time interval that can be measured. The RC time constant is the product of the resistance (R) and capacitance (C) in the circuit: RC = R × C, which also indicates the time required for the voltage across the capacitor to either charge or discharge to approximately 63.2% of its final value. In order to measure smaller time variations, it is necessary to reduce the RC time constant.
To achieve this, one should either decrease the resistance (R), decrease the capacitance (C), or both. Since the question asks for the manipulation of both R and C, the correct approach would be option (b) Decrease both R and C. By reducing the resistance, the circuit allows for a faster response time. Likewise, by reducing the capacitance, the time it takes to charge and discharge the capacitor becomes shorter, allowing the circuit to accurately track rapid voltage changes like those seen in an ECG.
Specifically, for ECG monitors, having a smaller RC time constant allows the equipment to detect rapid changes in heart activity, which is crucial for accurate monitoring and diagnosis. Therefore, in practice, it is vital to adjust R and C to values that ensure the time constant is less than what is required by the measurement system.