Question

An ammeter is always connected in series in a circuit because
A. its resistance is very high
B. its resistance is very low
C. it does not draw current from the circuit
D. its resistance infinity

Answer 1

Hint: An ammeter is a measuring instrument used to measure the current in a circuit. Electric currents are measured in amperes; hence the instrument used to measure electric current in amperes is called an ammeter. We will study about the construction and working of an ammeter so as to find the reason why it is always connected in series in a circuit.

Complete step-by-step answer:
Meter is associated with the measurement system. Meter is an instrument that can measure a particular quantity. As we know, the unit of electric current is Ampere, Ammeter means Ampere-meter which measures ampere value. Ampere is the unit of current so an ammeter is a meter or an instrument which measures electric current in a circuit.
Ammeter is an instrument for measuring either direct or alternating electric current passing through a circuit, in amperes. An ammeter has the capability to measure a wide range of current values because at high values of electric current, only a small portion of the current is directed through the meter mechanism as a shunt connected in parallel with the meter carries the major portion of that current.

Working Principle of an Ammeter:
The main principle for the working of an ammeter is that it must have a very low resistance and also the inductive reactance. It has very low impedance in order to have very low amount of voltage drop across itself when used in a circuit and must be connected in series connection because the current remains the same in the series circuit.
Also due to very low impedance, the power loss through an ammeter will be low and if it is connected in parallel it will become a short circuited path and all the current will flow through the ammeter and as a result of high current the instrument may damage. So due to this reason, the ammeter must be connected in series in a circuit.
An ammeter is always connected in series in a circuit because its resistance is very low.

So, the correct answer is “Option B”.

Note: Ammeter is a device obtained by connecting a very small resistance in parallel with a galvanometer. Since in a parallel combination, the equivalent resistance of the combination is always less than the smallest resistance, hence, the ammeter has negligibly small resistance. As a result of this, an ammeter allows the passage of maximum of the main current in the circuit and hence, it is connected in the series in a circuit in order to get the accurate current reading.
For an ideal ammeter, it must have zero impedance so that it has zero voltage drop across itself when connected in the circuit, and the power loss in the instrument will be zero. But the ideal ammeter is not practically achievable.