Loading Effect (2)

This content contains a detailed explanation of the loading effect of the ammeter.

Loading Effect of Ammeter

Before answering the question of what is the loading effect of the ammeter, let's briefly explain what is the ammeter and what are its features.

Ammeter is a measuring instrument that allows us to measure the current flowing in a circuit. The internal resistance of the ammeter is very small. Therefore, it must be connected in series with the circuit. If the ammeter is connected in parallel to the circuit, infinite current flows through it. This situation both prevents measurement and causes the ammeter to break down.

The loading effect of the ammeter can be explained as follows. The difference between the current value measured before the ammeter is connected to a circuit and the current value measured after the ammeter is connected is defined as the loading effect of the ammeter.

Let's explain it with a simple example to better understand the loading effect of the ammeter.

Example:

• In the first step, let's build a circuit and then calculate the total current of the circuit. The circuit is shown below.

OHM's law is used to calculate the total current of the circuit.

OHM's Law:

V = I.R

V is the source V₁ to which voltage is supplied to the circuit. R is the resistor R₁ that provides resistance to the circuit. I is the total current of the circuit.

V₁ = I. R₁

100 mV = I. 100 Ω

I = 1 mA

• In the second step, let's connect an ammeter to the circuit. Let's assume the internal resistance of the ammeter we connected is 100 Ω. The circuit is shown in the figure.

Similarly, OHM's law is used to find the total current in the circuit.

OHM’s Law:

V₁ = I . (R₁ + 100 Ω)

100 mV = I . (100 Ω + 100 Ω

100 mV = I . (200 Ω)

I = 0.5 mA

As shown in the calculations, the total current of the circuit was 1 mA before the ammeter was connected. But change it to 0.5 mA after the ammeter is connected. This difference between the two calculations is called the loading effect of the ammeter.

>>> In the next article, how to calculate the loading effect will be shown with examples.