Ammeter
An instrument used to measure currents is called an ammeter. To measure the current in a wire, you usually have to break or cut the wire and insert the ammeter so that the current to be measured passes through the meter.
The principle of operation of ammeters is based on the interaction between an electric current and a magnetic field. Ammeters are typically designed as a low-resistance device that is placed in series with the circuit being measured.
Analog and digital ammeters are two types of devices that are used to measure electric current.
Here are three examples of electric currents that can be measured by ammeters:
- Household circuits: The current flowing through a typical household circuit in the United States is 15-20 amperes.
- Automotive circuits: The current flowing through the battery or alternator of a car is typically 50-150 amperes.
- Small electronics: The current flowing through the power supply of a small electronic device, such as a cell phone or laptop, is typically 0.1-1 ampere.
Voltmeter
Voltmeters are instruments used for measuring the electric potential difference between two points in an electric circuit. To find the potential difference between any two points in the circuit, the voltmeter terminals are connected between those points without breaking or cutting the wire.
ΔV = Va – Vb
The most common types of voltmeters are:
- Permanent Magnet Moving Coil Voltmeter – PMMC
- Moving Iron Voltmeter
- Digital Voltmeter – DVM
- Electrodynamometer
- Rectifier Type Voltmeter
- Induction Type Voltmeter
- Electrostatic Type Voltmeter
Ammeter–voltmeter method for measuring resistance
The ammeter-voltmeter method is a technique used to measure the resistance of an electrical component. It involves using an ammeter and a voltmeter in a circuit with the component whose resistance is to be measured. Here are the steps to follow:
- Disconnect the power source from the circuit.
- Connect the ammeter in series with the component whose resistance is to be measured.
- Connect the voltmeter in parallel with the component.
- Reconnect the power source to the circuit.
- Read the current on the ammeter and the voltage on the voltmeter.
- Use Ohm’s Law (R = V/I) to calculate the resistance of the component, where R is the resistance, V is the voltage across the component, and I is the current through the component.
Ammeter and Voltmeter in Hydraulic Analogy
An instrument used to measure currents is called an ammeter. To measure the current in a wire, you usually have to break or cut the wire and insert the ammeter so that the current to be measured passes through the meter. An ammeter always measures the current passing thr
In the hydraulic analogy, an ammeter can be represented by a flow meter, which measures the rate of fluid flow in a pipe. The greater the flow rate, the higher the reading on the flow meter, just like how an ammeter measures the flow of electric current in a circuit.
On the other hand, a voltmeter can be represented by a pressure gauge, which measures the pressure of fluid in a pipe. The greater the pressure, the higher the reading on the pressure gauge, just like how a voltmeter measures the potential difference or voltage in an electric circuit.
Therefore, in the hydraulic analogy, an ammeter measures the flow of fluid, while a voltmeter measures the pressure of fluid. Both are important in understanding the behavior of fluid systems, just as ammeters and voltmeters are important in understanding the behavior of electric circuits.
