Question

The resistance of a pure copper wire of length 10 cm and diameter 1 mm is to be measured. The most suitable method from amongst the choices given below is _________.

• A. Two wire method
• B. Three wire method
• C. Four wire method
• D. Ellipsometry

Hint:

The four-wire method provides the most accurate measurement of resistance by eliminating the effects of lead and contact resistance.

Answer 1

The Correct Option is C

Step 1: Understanding the measurement methods.
The measurement of resistance in a conductor can be affected by various factors such as the contact resistance and the resistance of the leads. The four-wire method is the most accurate as it eliminates the effect of lead and contact resistance, providing precise measurement of the wire's resistance. Step 2: Analyzing the options.
- (A) Incorrect, the two-wire method can lead to errors due to the resistance of the wires themselves.
- (B) Incorrect, the three-wire method is typically used to reduce errors caused by lead resistance, but it still does not eliminate them completely like the four-wire method.
- (C) Correct, the four-wire method involves using two wires to carry the current and two separate wires to measure the voltage, effectively eliminating the influence of lead and contact resistance.
- (D) Incorrect, ellipsometry is used for measuring film thickness and refractive indices, not for measuring resistance. Step 3: Conclusion.
Thus, the most suitable method for measuring the resistance of the copper wire is the (C) Four wire method.