To measure which of the following is an ammeter used?
Electric current
Understanding Electrical Measurement: What an Ammeter Measures
In the study of electricity and circuits, various instruments are used to measure different electrical quantities. One fundamental instrument is the ammeter, which plays a crucial role in analyzing circuit behavior.
What is an Ammeter?
An ammeter is an electrical instrument used specifically to measure the magnitude of electric current flowing through a point in a circuit.
- Electric Current: This is the flow of electric charge (usually electrons) through a conductor. It is typically measured in Amperes (A).
- The ammeter is always connected in series with the component or part of the circuit where the current is to be measured. This ensures that the same current that flows through the component also flows through the ammeter.
- Ideally, an ammeter should have very low resistance so that its presence in the circuit does not significantly affect the current being measured.
Analyzing the Options
Let's consider the options provided and determine which electrical quantity is measured by an ammeter:
| Option | Electrical Quantity | Instrument Used for Measurement |
|---|---|---|
| 1 | Electric current | Ammeter |
| 2 | Potential difference | Voltmeter |
| 3 | Resistance | Ohmmeter (or indirectly using Ammeter and Voltmeter) |
| 4 | Electric charge | Electrometer (typically for static charge) or derived from current and time |
Based on the function of the ammeter, it is designed to measure electric current. Other quantities like potential difference are measured by a voltmeter, and resistance is measured by an ohmmeter or can be calculated using Ohm's Law ($\text{V} = \text{IR}$) if voltage and current are known.
Connecting an Ammeter in a Circuit
Proper connection of an ammeter is essential for accurate measurement and to prevent damage to the instrument. An ammeter must be connected in series with the circuit element through which the current is being measured. For instance, to measure the current flowing through a resistor, the ammeter is placed in the path of the current before or after the resistor, ensuring the current flows through both the resistor and the ammeter sequentially.
Revision Table: Electrical Measurements
| Quantity | Definition | Standard Unit | Measuring Instrument | Instrument Connection |
|---|---|---|---|---|
| Electric Current | Rate of flow of electric charge | Ampere (A) | Ammeter | Series |
| Potential Difference | Energy per unit charge moved between two points | Volt (V) | Voltmeter | Parallel |
| Resistance | Opposition to the flow of electric current | Ohm ($\Omega$) | Ohmmeter | Typically measured when component is isolated |
| Electric Charge | Fundamental property of matter (excess or deficiency of electrons) | Coulomb (C) | Electrometer (for static charge) | Not directly measured by ammeter/voltmeter in circuits |
Additional Information on Ammeters and Current Measurement
- Ammeter range can vary greatly, from microamperes ($\mu\text{A}$) to kiloamperes ($\text{kA}$).
- Digital ammeters often provide a direct numerical reading, while analog ammeters use a needle moving across a scale.
- Connecting an ammeter in parallel with a circuit component is dangerous because it has very low resistance, which can cause a large current to flow through it, potentially damaging the ammeter or the power source.
- The direction of current flow is typically indicated by terminals (positive/negative or red/black) on the ammeter, though many modern digital ammeters can measure current flow in either direction and indicate polarity.
Important Questions from Basic DC Ammeter
The range of an ammeter can be extended by using:
Name the tool which is used to measure the current in any electronic circuit.
- Why we use low internal resistance in series of an ammeter?
A (0-50)A moving coil ammeter has a voltage drop of 0.1V across its terminals at full scale deflection. The external shunt resistance (in milliohms) needed to extend its range to (0 - 500 A) is –
Two ammeters x and y have resistances of 1.2 Ω and 1.5 Ω respectively and they give full scale deflection with 150 mA and 250 mA respectively. The ranges have been extended by connecting shunts so as to give full scale deflection with 15 A. The ammeters along with shunts are connected in parallel and then placed in a circuit in which the total current flowing is 15 A. The current in amperes indicated in ammeter x is-
