Question

The resistance of an ideal ammeter is:
A) Infinite
B) Very high
C) Small
D) Zero

Answer 1

We use devices to measure current flowing in an electrical circuit which is known as ammeter. We will discuss how an ammeter works and then the principle behind its resistance and how it is connected in a circuit.

Complete answer:
An ammeter or an ampere meter is a measuring instrument, used to measure current in a circuit which is measured in the unit of amperes. The ammeters used to measure current in smaller units are called micro-ammeters and milli-ammeters. Here are several types of ammeters used such as moving coil, electro-dynamic, digital etc. They all are connected in the circuit in a series connection. An ammeter if contains a considerably large amount of resistance then it will in turn increase the equivalent resistance of the circuit and cause in less amount of current flowing. So we will face errors in measurement. But if the resistance is somehow kept small from the beginning then the ammeter will have less impact on the equivalent resistance of the circuit and we will get less error in measurement. An ideal ammeter is an ammeter whose resistance is zero thus giving the user zero error in measurement. Practically there is no such conductor whose resistance is zero. But ammeters have very low resistances which causes very low error and which can be negligible.
So our correct answer is, option D, zero.

Note: This is it, the ideal ammeters, if they exist , should have zero resistance. Ammeter was invented by Orsted. There is another device used to measure the potential difference in the circuit called the galvanometer which is always connected in parallel with the circuit, and an ideal galvanometer should have infinite resistance.