# Voltage Readings: Internal Resistance & Measurement

In summary, when using a voltmeter to measure voltage drop across a resistor, the measurement shown will include the voltage drop caused by the internal resistance of the voltmeter itself. This is because the voltmeter is inserted in parallel with the load, resulting in the same voltage drop across both the internal resistance and the load. The circuit will draw a different current compared to the case with no voltmeter, and it is preferred to have a larger internal resistance to minimize this difference. The voltmeter relies on a galvanometer, a sensitive current reader, to measure the voltage drop, and the internal resistance of the voltmeter is not infinite, resulting in some leakage current. By carefully calibrating the current to voltage

I am having trouble understanding this concept. I know that a voltmeter has an internal resistance of its own. When using a voltmeter to measure the voltage drop across a resistor, does the measurement shown on the voltmeter INCLUDE the voltage drop caused by the internal resistance of the voltmeter itself?

the voltmeter is insert in parallel with the load that you are trying to measure, as a result, the v drop across the internal resistance will be same as the drop across the load. the only different when compare to the case with no voltmeter is that the circuit will draw a different current...that's why you want it to be as large as possible so that this difference would be small... since adding something in parallel changes the overall resistance. now, to measure voltage drop the voltmeter rely on a device called galvanometer (ie. a current reader) which is supposedly very sensitive to tiny current flow. since the internal resistance of a voltmeter is not infinite, some leakage current will flow through it, and therefore by carefully calibrating the current to voltage ratio, one can work out what is the voltage drop.

The voltmeters resistance is assumed to be infinate relative to the resistor being measured - this way non of the current flows through it. But in reality it's still finate so there may be very small differences between the voltage measured and the actual voltage. Since this difference is close to constant it can be factored into the result.

## What is voltage?

Voltage is a measure of the potential energy difference between two points in an electrical circuit. It is often referred to as electrical potential or electromotive force (EMF).

## What is internal resistance?

Internal resistance is the inherent resistance within a power source, such as a battery or generator. It is caused by the resistance of the materials used in the construction of the power source.

## How is voltage measured?

Voltage can be measured using a voltmeter, which is a device that measures the potential difference between two points in an electrical circuit.

## Why is it important to measure internal resistance?

Measuring internal resistance is important because it can indicate the health and efficiency of a power source. A high internal resistance can result in a lower voltage output and decreased performance.

## How does temperature affect voltage readings?

Temperature can affect voltage readings because it can impact the internal resistance of a power source. In general, as temperature increases, internal resistance also increases, which can result in a lower voltage output.