Any components placed in series where there are no junctions will have the same current through it.The ammeter must always be placed in series with the component.In a series circuit there is only one path for the charge carriers. Charge is conserved: it cannot be created, destroyed or piled up anywhere in the wire, so the charge passing each point every second must be the same all the way round. The current is the same at every point in a series circuit.Current is not "used up" by components. A lamp or resistor transfers energy from the charge carriers, but the same number of charge carriers leave it each second as enter it. What is shared between the components is the potential difference, not the current.Because an ammeter is connected in series, the whole current passes through it. An ideal ammeter therefore has zero resistance, so that connecting it does not change the current it is measuring.Worked exampleA cell, a lamp and a resistor are connected in series. An ammeter between the cell and the lamp reads 0.30 A. What do ammeters between the lamp and the resistor, and between the resistor and the cell, read? How much charge passes through the resistor in 20 s?
There are no junctions, so both ammeters also read 0.30 A.Q = It = 0.30 A × 20 s = 6.0 C The same 6.0 C passes through the lamp and the cell in that time.
There are no junctions, so both ammeters also read 0.30 A.