# How Does Electricity Flow In A Circuit Draw And Open Circuit?

An electric circuit is a complete loop through which electric current can flow. It includes a power source like a battery, components like resistors, inductors and capacitors, and connecting wires. The main job of a circuit is to distribute electricity from the power source to the components doing useful work, called the load. The load can be anything from a lightbulb to a smartphone.

Current is the flow of electric charge in a circuit. It is measured in Amperes (Amps). Voltage, measured in Volts (V), is the electrical potential energy per unit charge. Voltage is supplied by the power source like a battery and pushes current through the circuit, enabling the components to do work. Power, measured in Watts (W), is the rate at which the electrical energy is transferred in the circuit.

For a circuit to work properly, it must be a complete loop with no gaps. Electricity flows from the positive terminal of the power source through the components and back to the negative terminal. Any break in this loop will stop the flow of current and is called an open circuit.

## Circuit Diagrams

Circuit diagrams are visual representations that show how electrical components are connected together in a circuit. They use standardized symbols to represent each component, making it easy to visualize the flow of current through the circuit.

Some common symbols used in circuit diagrams include:

- Battery – Represents the power source. Long lines are positive terminals and short lines are negative.
- Wires – Used to connect components. Wires crossing without connecting indicate no connection.
- Resistor – Impedes current flow. Represented by a zig-zag line.
- Capacitor – Stores electric charge. Represented by two parallel lines.
- Inductor – Coils that induce voltage when current changes. Represented by a coiled wire.
- Switches – Open or close circuits. Represented by lines crossing.
- Lamps – Convert electricity into light. Represented by symbols that look like light bulbs.

Here is a simple example of a circuit diagram:

This diagram shows a battery connected to a lamp through wires and a switch. When the switch is closed, it completes the circuit so current can flow from the positive terminal of the battery through the switch, then the lamp, and back to the negative terminal.

Circuit diagrams provide a simple visual language to represent connections and components in an electrical circuit.

## Current in a Circuit

Current is the flow of electric charge in a circuit. It is measured in amperes (amps). In order for current to flow, there must be a closed circuit or loop. This means the circuit has no gaps or breaks in it. When the circuit is closed, electrons can flow continuously around the loop.

Conventional current flows from the positive terminal of the battery, through the circuit components, and back to the negative terminal. So the direction is from higher potential to lower potential. However, electrons themselves actually flow in the opposite direction, from negative to positive. But for simplicity, the conventional current model is used for most circuit analysis.

The amount of current depends on the voltage supplied and the resistance in the circuit. Using Ohm’s law, current is equal to voltage divided by resistance. A higher voltage or lower resistance allows more current to flow. Resistors limit current, while wires and other conductors allow current to flow easily.

In a series circuit, the current is the same at all points since it is a single loop. But in parallel circuits, the current splits among different branches, so it is not equal throughout. Understanding how current flows is key to properly designing, constructing and analyzing both simple and complex circuits.

## Voltage in a Circuit

Voltage is the electrical potential difference between two points in a circuit. It is a measure of the ‘push’ behind the flow of electricity. Voltage is analogous to the pressure of water flowing through a pipe in a plumbing system.

As current flows through the various components in a circuit, there will be a voltage drop across each component. This voltage drop is due to the resistance of the component. For example, as current flows through a resistor, there will be a voltage drop across the resistor according to Ohm’s law: V = IR, where V is voltage, I is current, and R is resistance.

The greater the resistance, the larger the voltage drop across that component for a given current flow. The total voltage in a circuit is the sum of all the individual voltage drops across each component.

Voltage can be measured by connecting the positive lead of a voltmeter in parallel across the component where the voltage drop is to be measured. The negative lead is connected to the more negative side of the component. The voltmeter will then display the voltage drop across that component.

Voltage polarity simply refers to the positive and negative orientation of a voltage source or drop. For example, the positive terminal of a battery is at a higher voltage potential than the negative terminal.

## Series Circuits

In a series circuit, the components are connected end-to-end in a loop so the same current flows through each component. The total voltage of the circuit is equal to the sum of the voltage drops across each component. For example, if a circuit contains a 9V battery and three resistors with voltage drops of 2V, 3V and 4V respectively, the total voltage is 9V and the current through each resistor is the same. The current can be calculated using Ohm’s law:

I = V/R

Where:

- I is the current in amps
- V is the total voltage in volts
- R is the total resistance in ohms

For the example circuit:

- V = 9V
- R = 2Ω + 3Ω + 4Ω = 9Ω

Therefore:

I = V/R = 9V/9Ω = 1A

The current throughout the entire series circuit is 1A. The voltage drops across each resistor can be calculated using Ohm’s law and the resistor values. This demonstrates how voltage divides across components in a series circuit, while current remains constant.

## Parallel Circuits

Parallel circuits contain branches or paths that current can follow. Unlike series circuits where current must flow through one path, in parallel circuits the current divides and flows through multiple paths. Each branch or path in a parallel circuit operates independently with its own voltage source and load. The branches are connected at junction points where the flow of current converges and diverges.

In a parallel circuit, the total current is equal to the sum of the currents through each branch:

Itotal = I1 + I2 + I3 + …

The voltage across each branch is the same as the voltage source. This is known as a parallel voltage divider rule:

Vsource = V1 = V2 = V3 = …

To calculate the total resistance in a parallel circuit, use the formula:

1/Rtotal = 1/R1 + 1/R2 + 1/R3 + …

Here is an example of a parallel circuit with two branches:

If the voltage source is 10 volts, R1 is 5 ohms, and R2 is 10 ohms, then:

I1 = V/R1 = 10/5 = 2 A

I2 = V/R2 = 10/10 = 1 A

Itotal = I1 + I2 = 2A + 1A = 3A

1/Rtotal = 1/5 + 1/10 = 0.2 + 0.1 = 0.3

Rtotal = 1/0.3 = 3.33 ohms

This demonstrates the basic principles and calculations for parallel circuits.

## Open Circuits

An open circuit is a circuit that has a break somewhere, preventing current from flowing properly. This break can occur anywhere in the circuit and stops the flow of electrons through the circuit. Some common causes of open circuits include:

- A wire is disconnected or loose
- A switch is turned off
- A fuse is blown
- A component has failed

With an open circuit, the path for current flow is incomplete. This means that even if voltage is applied, no electrons will be able to flow and no current will exist in the circuit. An open circuit has infinite resistance because of the break in the conductive pathway. Essentially, an open circuit acts like a switch in the “off” position.

Some effects of an open circuit include:

- All components stop working since current can’t flow through them
- The circuit does not function as intended
- No power is transferred to devices and components
- Voltage measured across an open break reads 0V

For example, if a light bulb circuit has a broken filament in the light bulb, this creates an open circuit. Current can’t flow to light the bulb. Turning off a switch also opens the circuit, preventing current from reaching the light.

## Short Circuits

A short circuit occurs when two nodes of a circuit are connected by a conductor with little to no resistance. This provides a path for the current to flow through with no load or work. In a short circuit, the current bypasses the load and flows directly between the power source terminals. This results in an excessive amount of current flow since there is no resistance to limit it.

Short circuits are usually caused by faults in wiring, such as loose connections, damaged insulation, crossed wires, or excessive moisture or dirt buildup providing conductivity between exposed conductors. Other causes can include manufacturing defects, poor design, component failure, accidents, or damage from external factors.

The effects of a short circuit can be dangerous, resulting in overheating of conductors, damage or destruction of equipment, fire hazards, and circuit breaker tripping. The excessive current flow can also quickly drain the battery or generator supplying the power.

Some examples of short circuit scenarios:

- Bare wires touching each other due to worn insulation
- Nails or screws puncturing wires inside a wall
- Conductive metal falling across the terminals of a battery
- Damaged power cords bridging positive and negative prongs
- Electronics submerged in water causing uncontrolled current flows

In circuit design and analysis, short circuits are often intentionally created to simplify calculations and measurements. But in general circuits, short circuits are hazardous and should be avoided through proper design, maintenance, and safety practices.

## Circuit Analysis

Circuit analysis involves studying and understanding what is happening inside an electric circuit. Some key methods used to analyze circuits include:

**Ohm’s Law**

Ohm’s Law describes the relationship between current (I), voltage (V), and resistance (R) in an electric circuit. It states that the current through a conductor is directly proportional to the voltage across the conductor, for a given resistance. The equation is:

V = IR

Where V is voltage measured in volts, I is current measured in amps, and R is resistance measured in ohms. Ohm’s Law allows calculation of any one quantity given values for the other two. For example, if the voltage is 120V and the resistance is 40Ω, then using Ohm’s Law the current would be 3A (120V/40Ω = 3A).

**Kirchhoff’s Laws**

Kirchhoff’s Laws allow more complex circuits with multiple branches and loops to be analyzed. Kirchhoff’s Current Law (KCL) states that the sum of all currents entering and leaving a node must equal zero. Kirchhoff’s Voltage Law (KVL) states that the voltages around any closed loop must equal zero. By applying these laws, the currents and voltages at different points in a circuit can be found.

For example, in a circuit with three branches, KCL could be used at the node connecting them to find the current in the third branch given the currents in the first two. KVL could then be applied around a loop containing the third branch to determine the voltage.

**Load and Power Calculations**

Load and power calculations analyze the power usage in a circuit. The current draws of individual components are summed to find the total load current. Using Ohm’s Law and the total resistance, the load voltage can be found. Finally, power is calculated using:

P = IV

Where P is power in watts, I is load current in amps, and V is load voltage in volts. These calculations ensure the power source is sized appropriately for the expected load.

## Conclusion

To summarize, electricity requires a closed loop path called a circuit in order to flow. Circuits provide this path, allowing electric current to flow from the positive terminal of the power source through the wires and components and back to the negative terminal. An open circuit breaks this loop, preventing current from flowing. The key differences between closed circuits and open circuits are:

- Closed circuit – allows electricity to flow continuously as it provides a complete loop path. Current flows, components operate.
- Open circuit – breaks the loop path for electricity. Current cannot flow, components cannot operate.

Understanding the basic principles of how electricity flows in circuits provides an important foundation for working with electrical and electronic systems.