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Voltmeter Ammeter method is use for measurement of ?
Winding resistance
Insulation resistance
Both
None of above
Winding resistance
The Voltmeter-Ammeter method is a standard technique used to measure low to medium range resistances, such as transformer or motor winding resistances. It involves measuring the voltage drop (V) across the unknown resistance (R) and the current (I) flowing through it, then calculating the resistance using Ohm's Law.
The Voltmeter-Ammeter method is a standard technique used to measure low to medium range resistances, such as transformer or motor winding resistances. It involves measuring the voltage drop (V) across the unknown resistance (R) and the current (I) flowing through it, then calculating the resistance using Ohm's Law.
R=IVтАЛ тАФ Determination of resistance using measured voltage and current
The circuit consists of a DC source, an ammeter connected in series with the resistor, and a voltmeter connected in parallel with it. By applying Ohm's Law R=IVтАЛ, the resistance is determined. For low resistance measurements, the voltmeter is placed directly across the component to minimize error from ammeter voltage drop.
Used primarily for low to medium value resistors.
Accuracy depends on the internal resistance of the meters used.
Requires a DC power supply to avoid complications from inductive or capacitive reactance.
Suitable for field testing of transformer windings.
Simple to implement
Direct measurement based on fundamental Ohm's Law
Potential errors due to loading effect of meters
Not suitable for very high resistance (insulation resistance)
Transformer winding resistance testing
Motor armature resistance measurement
Insulation resistance is measured using a Megger (High voltage DC insulation tester) because it requires much higher voltage levels to detect leakage.
For very low resistances, the Kelvin Double Bridge is preferred over the Voltmeter-Ammeter method.
A is correct тАФ The Voltmeter-Ammeter method is specifically designed for determining the low DC resistance of electrical windings.
Always remember: Megger for Insulation (High R), Wheatstone/Kelvin bridge or V-A method for Winding Resistance (Low R).