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Homework → Science → Physics → Electric Symbols
When drawing electric circuits, symbols are used:
|
A cell |
A battery of 3 cells |
A 6v battery of cells |
Lamp 1 |
Lamp 2 |
| Switch (SPST) |
Push Button Switch |
Fixed Resistor |
Variable Resistor |
Fuse |
| Diode |
Ammeter (Connect in Series) |
Voltmeter (Connect in Parallel) |
Motor |
Buzzer |
Current
Current (unit Amps, A) is a measure of the rate of flow of electrons around a circuit. For current to flow there must be a continuous chain of electrons around a circuit. Therefore if there is a gap in the circuit, there will be no current. Conventional current flows from positive to negative around the circuit. You can show the direction of current using an arrow.
You can use various different methods to measure the amount of current flowing around a circuit. You could do so by using the brightness of a lamp, the speed of a motor or the loudness of a buzzer. However, these methods are inaccurate, it is far better to use an Ammeter. This records the number of Amps (A) passing through the circuit at a specific point. An ammeter is connected in series with the positive (red) side facing the positive side of the cells.
To represent the direction of current you use an arrow and the letter "I", which represents current.
Voltage
Volatage (units Volts, V) can also be called "potential difference". It is the voltage of a battery or cell that pushes the current around the circuit (opposites poles on the cell attract). As the current flows, energy (NOT current) is used to power the bulbs or buzzers etc. and so energy at the start is greater than the energy at the end. An instrument called a voltmeter is used to measure voltage. This is connected in parallel across any component in the circuit.