why is a potentiometer considerd as voltmeter with an infinite resistance
The correct answer and explanation is :
A potentiometer is considered a voltmeter with infinite resistance because it is designed to measure potential difference (voltage) without drawing any current from the circuit. To understand why this is the case, we need to first look at the working principles of a potentiometer and the characteristics of a voltmeter.
The Working Principle of a Potentiometer:
A potentiometer is a variable resistor used to measure the potential difference between two points in an electrical circuit. It consists of a resistive element (usually a wire or track) and a sliding contact (or wiper). The resistance of the potentiometer can be adjusted by moving the wiper along the resistive element, allowing it to vary the potential at different points along the element.
When used in a circuit to measure voltage, the potentiometer is connected in such a way that no current is drawn from the circuit under measurement. Instead, the potentiometer is adjusted until the voltage across it matches the voltage between the two points in the circuit. At this point, the current through the potentiometer is essentially zero, meaning it does not influence the circuit it is measuring.
Infinite Resistance of the Potentiometer:
In an ideal voltmeter, the resistance should be infinitely high so that it does not draw any current from the circuit it is measuring. If a voltmeter draws current, it would alter the voltage across the components in the circuit, leading to inaccurate readings. The potentiometer functions in a similar manner. When measuring voltage, it does not draw any current from the circuit, which means its internal resistance must be very high, ideally infinite.
The key reason a potentiometer is considered a voltmeter with infinite resistance is that it allows for voltage measurement without interfering with the circuit, which is a defining characteristic of an ideal voltmeter. By not drawing any current, it ensures that the voltage being measured is not altered or disturbed by the measurement process itself.