Electric Circuits

It is said that the electric potential causes the electrical charges to move. These charges distribute the energy they carry from the source to the different loads they may encounter along their path or along the conductor where they flow. In order for them to deliver these energy, the load must be connected to the power supply or the electric potential. We call this connection, electric circuit.

In physics, circuit diagrams to represent and illustrate electric circuits. In a circuit diagram, the current flowing through the circuit, the resistance of the electrical loads and the source of electric potential are indicated and the parts of the circuit are represented by electrical symbols. Here are some symbols often used in some physics problems.

Source of Electric Potential

Cell Cells in Series (Battery)


Electrical Loads


Lamp Resistor


There are two types of electric circuits - Series Circuit and Parallel Circuit.



Series Circuit is a type of connection wherein from the source, the electron flows in a single path going to the loads before going back to the source. This means that if there are at least 3 loads connected to the source, the electric charges will pass through each of the loads in the circuit following the same path before going back to the source as shown below.


Lamps in Series Resistors in Series


On the illustration above, the arrows indicate the flow of electric charges from one load to another. As you can see, the charges move in a single path passing through each of the loads and back to the source. 

In this type of circuit, all the loads receive the same amount of electric current.

Here are some advantages and disadvantages of a series connection.

1. Since the loads are connected by a single wire, series circuit is easier to build up. 1. Since the charges flow in just a single path, all loads might not function if anyone of the loads malfunctioned or destroyed.
2. Series circuit do not overheat easily. 2. The more loads, the greater the resistance of the circuit.
3. Easy to add additional power devices.  



In a Parallel Circuit the electric charges reach each load moving or passing through different path. Each load has its corresponding path from the source. The electrons may flow from load to load one at a time, depending on which path it will take first and then go back to the source. Meaning, the charges have a choice to which path it will take. See illustration below.



Lamps in Parallel Resistors in Parallel


The arrows represent the flow of charges. Each group of arrows represent different path. The electrons have a choice to which path it will take.

In this connection, the loads will receive different amount of  electric current.

The table below lists down some advantages and disadvantages of parallel circuit.

1. Since the charges have a choice to which path it will take, the other loads will still work even if any of the loads malfunctions or destroyed. 1. Connecting loads in parallel is complicated. A lot of wires are needed to connect each load to the power supply.

2. Loads can be easily connected or disconnected                without affecting the other loads in the circuit.

2. Since the loads have the same electric potential, it is more difficult to add more power supply.
3. The amount of electric potential is the same all throughout the connection.