The loading effect of electrical instruments is defined as the degree to which the electrical measurements impact the electrical properties of a circuit. These measurements are mainly ammeter, voltmeter, and a multimeter.

In electrical measurements mainly three types of instruments included such as ammeter, voltmeter, and a multimeter. So let’s discuss the loading effect of all these three instruments.

An ammeter is an electrical instrument that measures AC or DC in Amperes. To measure the current flow in a given electrical circuit, the ammeter should be connected in series. The ammeter is designed for small internal resistance (10 – 100 Ω). Now for impact working of an ammeter, there are two possible cases exists:

Case-1:

In this case, the ammeter is connected to a low resistance circuit then the overall resistance of the circuit is dragged to a noticeable amount. So, this means that when an ammeter having a value of 50 ohms internal resistance is connected to a 100 ohms circuit then finally its value is rapidly increased to 3 times. So this finally results in an increase in voltage as well as current by 3 times.

Case-2:

Now on the other hand when the internal resistance of the ammeter is high the same value of impact is observed. And the parameter of an electrical circuit changes or varies.

A voltmeter is also an electrical device, this gives the potential difference between two points of an electrical circuit. A voltmeter is always connected in parallel with the electronic components for measuring the voltage. Voltmeters are designed especially for high internal resistance. It’s valued generally range from (10-20) MΩ. For voltmeter also two possible cases exist:

Case-1:

When we connect a voltmeter to high external resistance it overall value rapidly decreases. Let’s consider an example of connecting the voltmeter to external resistance of 10 MΩ and internal resistance of the circuit to 7.5 MΩ resistors in parallel. Then it is observed that the overall resistance changes to 4.279 MΩ.

Case-2:

In the second case, it’s observed that when the internal resistance is small and connected to high external resistance then it is observed that overall resistance is seen to be changed.

As we have observed in the above both cases change the working of the circuit thus we get appropriate results from the measuring instruments.

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