How is the ammeter connected in all circuits to measure current flowing in it?
In series
Ammeter Connection for Measuring Current in Circuits
When we want to measure the electric current flowing through a part of a circuit or the entire circuit, we use an instrument called an ammeter. An ammeter is specifically designed to measure the rate of flow of electric charge, which is what current is.
The way an ammeter is connected in a circuit is crucial for it to correctly measure the current. Electric current flows along a specific path. To measure the current flowing *through* a point or a component, the ammeter must be placed directly in that path so that the current flows *through* the ammeter itself.
Let's consider the common ways components are connected in a circuit:
- Series Connection: Components are connected end-to-end, forming a single path for the current to flow. The current is the same at every point in a series circuit.
- Parallel Connection: Components are connected across the same two points, providing multiple paths for the current to flow. The voltage is the same across components in parallel.
If an ammeter were connected in parallel with a component, most of the current would bypass the component and flow through the ammeter (since an ideal ammeter has very low resistance), or worse, it could short-circuit the component or the power source, potentially damaging the circuit or the ammeter. This would not give an accurate measurement of the current flowing *through* the component or the intended path.
Therefore, to measure the current flowing through a specific point or component, the ammeter must be placed directly in the path of the current. This means the circuit must be broken, and the ammeter inserted into the break, becoming a part of the single path through which the current flows. This type of connection is known as a series connection.
In simple terms, think of current as water flowing in pipes. To measure the flow rate of water passing through a specific pipe, you need to cut the pipe and insert the flow meter directly into the line so all the water passes through it. Connecting the flow meter across the pipe (in parallel) would divert some water or cause problems.
Thus, the standard and correct way to connect an ammeter to measure current in any circuit is in series with the component or section of the circuit through which the current is to be measured.
Consider a simple circuit with a resistor and a battery. To measure the current through the resistor, the ammeter is placed in series with the resistor and the battery, in the main loop of the circuit.
Comparing Connection Methods for Ammeters
| Connection Type | How it Works | Effect on Circuit / Measurement | Suitability for Ammeter |
|---|---|---|---|
| Series (In line) | Ammeter is placed directly in the path of current flow. Current flows through it. | Measures the current flowing through that specific point or component accurately. Ammeter resistance is ideally zero. | Suitable and Correct Method |
| Parallel (Across) | Ammeter is placed across a component or points, creating an alternative path. | Current divides. Most current goes through the low-resistance ammeter. Does not measure the current through the component. Can damage circuit. | Unsuitable and Incorrect Method |
Based on the function of an ammeter and how current flows in a circuit, it must be connected in series (or "in line") with the circuit element through which the current is being measured. Both "in line" and "in series" essentially describe the same correct method in this context.
Ammeter Connection Summary
- An ammeter measures electric current ($\text{I}$).
- Current flows through a specific path in a circuit.
- To measure the current flowing through a point, the ammeter must be inserted into that path.
- This insertion is called a series connection.
- Connecting an ammeter in parallel is incorrect and can be harmful.
Revision Table: Electrical Measurement Instruments
| Instrument | Quantity Measured | Ideal Resistance | How Connected |
|---|---|---|---|
| Ammeter | Electric Current ($\text{I}$) | 0 $\Omega$ (ideally) | In Series |
| Voltmeter | Electric Voltage ($\text{V}$) | $\infty$ $\Omega$ (ideally) | In Parallel |
Additional Information: Ideal vs. Real Ammeters
An ideal ammeter would have zero resistance. This is because when it is connected in series, it should not affect the amount of current flowing in the circuit. If the ammeter had significant resistance, adding it to the circuit would increase the total resistance, thereby decreasing the current being measured ($\text{I} = \text{V}/\text{R}_{total}$).
Real ammeters have a very small, but non-zero, internal resistance. Modern digital ammeters are designed to have very low resistance to minimize their impact on the circuit and provide an accurate reading.
This low resistance further explains why connecting an ammeter in parallel is wrong. In parallel, current tends to follow the path of least resistance. If a low-resistance ammeter is placed in parallel with a component, most of the current will divert through the ammeter instead of the component, leading to an incorrect measurement and potentially damaging the circuit due to excessive current flow through the ammeter.
Important Questions from Current Electricity
_______ is a simple device that is used to either break the electric circuit, or to complete it.
When the material is cooled down under its critical temperature, which of the superconductor attains accidentally zero?
The most commonly used electrical conductor is-
The gas usually filled in the electric bulb is
_________ is the physical quantity of the substance which is numerically equal to the resistance of a rod of that substance which is 1 m long and 1 sq m in cross-section.
