P2bL6 Components in Series
Key Words
Battery - a number of cells. Often used to mean a single cell.
Components - items that make up the circuit.
Continuous Circuit - a complete circuit in which an electric current can flow.
Net potential - the total voltage.
Potential Difference - voltage.
Resistance - the extent to which components oppose the flow of current.
Series - components one after the other in a line.
Grade E
Think about this circuit consisting of three identical lamps.
If we start with one lamp, it glows brightly. If we add a second lamp, the two lamps glow less brightly. With a third lamp they are even dimmer. They are sharing the voltage.
This is a series circuit. The electrons have to go through the lamps in turn.
If we move the ammeter to different places in the circuit, we find that the current is the same, which gives us an important rule for series circuits:
In a series circuit, the current is the same, wherever in the circuit it is measured.
In other words, if the current is 1 amp at the ammeter, it would be 1 amp wherever we put the meter.
Grade C
Look at this circuit in which we will measure the voltage across each bulb.
The total voltage is V4. If we measure the voltages V1, V2, and V3, we find that they add up to the battery voltage V4. This gives us an important rule for a series circuit:
The potential differences across all the components add up to the battery potential difference.
We can also put cells in series to make higher voltages.
If each cell has a potential difference of 1.5 volts, we can see that the net potential (total voltage) is 1.5 + 1.5 + 1.5 = 4.5 volts in the battery above. This is because each positive terminal is connected to the negative in the next cell. Now if we turned one of the cells round, we would get:
In this case, cells A and B are opposing each other. So the potential difference between them will be 1.5 + - 1.5 = 0 V. Therefore the net potential will be 1.5 volts.
Grade A
The resistances in a series circuit add up:
Rtot = R1 + R2 + R3