Unknown Resistance to be Measured
Resistance R4 in a circuit is known as the "unknown resistance to be measured" because its value is not provided or predetermined. Instead, it is the resistor whose resistance needs to be determined using measurement techniques.

Importance of Resistance R4
- Resistance R4 plays a crucial role in various electronic circuits where its value needs to be accurately measured for proper functioning.
- Measuring Resistance R4 accurately ensures the overall performance and efficiency of the circuit.

Measurement Techniques
- Different methods such as Wheatstone bridge, Ohmmeter, and multimeter are commonly used to measure the resistance of unknown resistors like R4.
- These techniques involve applying known voltages and currents to the circuit containing R4 and then calculating its resistance based on the resulting readings.

Applications
- Resistance R4 is commonly found in sensor circuits, voltage dividers, and various electronic devices where precise resistance values are required.
- Accurate measurement of R4 is essential for calibration, troubleshooting, and maintenance of electronic systems.
In conclusion, resistance R4 is referred to as the "unknown resistance to be measured" in a circuit, and its accurate determination is vital for the proper functioning of electronic devices and systems. Various measurement techniques can be employed to determine the resistance of R4, ensuring the reliability and performance of the overall circuit.