Components of an Electrical Circuit !

Components of an Electrical Circuit !
Components of an Electrical Circuit !
Components of an Electrical Circuit !
Components of an Electrical Circuit !
Components of an Electrical Circuit !
Components of an Electrical Circuit !
Components of an Electrical Circuit !
Components of an Electrical Circuit !
Components of an Electrical Circuit !

A simple electrical circuit consists of the following components: 

  • Voltage or current source (e.g. a battery or power supply)
  • Consumer or load (e.g. incandescent lamp)
  • Connections between the voltage source and the load (e.g. cables/leads)
  • A switch to open and close the circuit (may be omitted)

If the load is connected to the voltage source via leads, the circuit is closed and a current flows from the voltage source through the load.

The following interactive animation enables you to set up a simple circuit. Drag and drop the individual components (1: voltage source, 2: load, 3: switch) to their respective locations in the circuit and switch the circuit on by actuating the switch.

Components of an Electrical Circuit !

In electrical engineering, circuits are usually depicted in a technical drawing known as a circuit diagram, whereby the individual components are represented by standardised symbols (circuit symbols). The following graphic shows the circuit diagram corresponding to the circuit above. Here additional pointer arrows have been included to show the directions of the source voltage U and the current I being conducted.

Components of an Electrical Circuit !

Measuring Voltage:

 

Electrical voltage is measured with a voltmeter. The following graphics show the circuit symbol of a voltmeter (left), an example of an analog voltmeter as found in a motor vehicle where it is used to display the battery voltage (centre) and a conventional multimeter, which may be used to measure voltage and other properties and is normally provided with a variety of measurement ranges.

Components of an Electrical Circuit !

To perform the measurement the voltmeter has to be connected to the voltage to be measured. A voltage can only ever exist between two points, e.g. between the terminals of a voltage source or a load. To measure this the voltmeter is connected parallel to the component, across which the voltage is to be determined. The following animation illustrates this. 

Components of an Electrical Circuit !

The following circuit diagrams demonstrate how the voltmeter is connected to measure various voltages in the simple circuit already considered. The circuit diagram on the left shows how the voltmeter should be connected to measure the source voltage, the circuit diagram in the centre shows how the instrument is connected to measure voltage across a switch and the diagram on the right shows how to connect it to measure the load voltage. 

Components of an Electrical Circuit !

Measuring Current:

Direct current measurement:

Electrical current (i.e. current intensity) is measured using an ammeter. The following graphic shows the circuit symbol of an ammeter. Conventional multimeters normally feature both a voltage measurement mode and an ammeter operating mode with various measurement ranges. 

Components of an Electrical Circuit !

 

To measure the current, the current that needs to be measured must pass through the ammeter. This means a gap needs to be made in the circuit and the ammeter connected in that space. Unlike a voltmeter an ammeter is located in series in the branch for which the current is to be measured. The subsequent animation illustrates this. 

Components of an Electrical Circuit !

The following circuit diagram shows various possibilities for integrating the ammeter into the simple circuit previously studied. Since this circuit comprises only one branch and the current is therefore the same at all points, it does not matter where the ammeter is inserted into the circuit. 

Components of an Electrical Circuit !

Indirect current measurement:

If there is no ammeter available for current measurement, only a voltmeter, then you can still determine the current indirectly by measuring the voltage. To do this we have to utilise the relationship between current and voltage across the load - which we will later encounter as Ohm's law. The principle is based on first inserting a small resistor RM into the circuit instead of an ammeter ("a shunt resistor") purely for the measurement. To ensure that this resistor has little impact on the current to be measured, it must have a very low value (e.g. 1 W). Then we use the voltmeter to measure the voltage UM across this "shunt". This then allows us to determine the current I according to the following relationship.

Components of an Electrical Circuit !

The following circuit diagrams reiterate the principle once again: the graphic on the left shows how the current is measured directly using the ammeter, while the graphic on the right shows the indirect measurement using a measurement shunt RM and a voltmeter. 

Components of an Electrical Circuit !

 

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