Circuits A circuit is a loop of wire with its ends connected to an energy source such as a cell* or a battery*.

One end of the wire is connected to the positive terminal The other end of the wire is connected to the negative terminal. The wire is connected in this way so a current* can flow through it.

Series Circuits Series circuits are the simplest type of circuits. Series circuits have all their parts connected in one loop of wire. On the right is a series circuit consisting of a cell and a lamp:

The series circuit below connects a cell*, a lamp and an ammeter*. The ammeter reads that the current through the lamp is 1.5 A.

And here is a series circuit consisting of a cell and two lamps: Notice that all the components are connected in one loop of wire.

Disadvantages of Series Circuits 1st: If one component in a series circuit fails, then all the components in the circuit fail because the circuit has been broken. 2nd: The more components there are in a series circuit, the greater the circuit's resistance*.

In the series circuit below, Ammeter 1 shows a reading of 1.5 A. What will be the readings on Ammeter 2 and Ammeter 3? Choose one : 0.5 A and 1.0 A 1.5 A and 1.5 A 1.5 A and 0.0 A

Well done! Ammeter 1, Ammeter 2 and Ammeter 3 each show the same reading of 1.5 A. A series circuit has just one current.

Parallel Circuits A parallel circuit is rather like two or more series circuits connected to the same energy source. For example, here is a parallel circuit connecting a cell* and two lamps:

And here is a parallel circuit connecting a cell and three lamps: Notice that the components lie inside "parallel" loops connected to the same energy source.

Parallel circuits have two advantages A failure of one component does not lead to the failure of the other components. More components may be added in parallel without the need for more voltage*.

The more components connected in parallel, the more energy is used. For example, if each of the circuits on this page used the same type of cell* and same type of lamp... ...this circuit would light one lamp for 12 hours:

the circuit below would light two lamps for 6 hours:

and the circuit below would light three lamps for 4 hours:

A cell provides enough energy to light either a blue lamp or a red lamp for six hours. For how long will the same cell light both lamps in parallel? Choose one answer below: 4 hours 2 hours 3 hours

Well done! The cell will light both lamps for 3 hours.

Current in Parallel Circuits Whereas the current flowing through a series circuit is the same everywhere, the current flowing through a parallel circuit depends upon where in the circuit the current is measured.

Ammeter 1 reads 1.5 A flowing through Lamp 1. Ammeter 2 also reads 1.5 A as Lamp 2 is identical to Lamp 1.

Now we connect a third ammeter next to the cell: What current will Ammeter 3 read?

Ammeter 3 reads 3 A Ammeter 3 reads 3 A. This is because the total current* flowing from a cell* in a parallel circuit equals the sum of all the currents flowing in the loops.

Ammeters 1, 2, and 3 read 1 A. Assuming all the lamps are identical, what will Ammeter 4 read?

Ammeter 3 reads 3 A. The total current flowing from a cell in a parallel circuit equals the sum of all the currents flowing in the loops.