When we talk about current, the one thing we often think about is electricity. This is true because we use electricity almost everywhere, and the basic concept of electricity is about the current or flow of electricity. In a simple circuit, a power source allows the flow of electricity through a pathway made of electrically conductive material where electricity can move through it. This flow of electricity moves until it reaches a load or a device being powered by the power source. Electricity continues to flow back into the positive terminal of the power source, which allows a loop to occur.
I. Principles
A circuit is the path in which current flows. Itโs kind of cool when you think about it. The principle is similar to how blood flows from the heart and returns to it. The battery is our power source, where the electrons come from. Through electrically conductive materials such as metallic wires, electrons can move from the negative terminal of the battery up to the load with the use of conductive pathways such as wires. Electrons release electrical energy that continuously flows out of the bulb without turning it off and goes straight to the battery's positive terminal. One underlying principle in electricity is called a potential difference.
A. Potential Difference
Batteries have positive and negative terminals. We see it as the battery's two ends with a plus and minus sign. This indicates a difference in the energy in both ends. Potential difference or voltage serves as the driving force of electron flow. The positive terminal (or cathode) has a high electric potential, whereas the negative terminal (anode) has a lower electric potential. As a response to this potential difference, electrons naturally move from an excess of electrons (anode) to a point with an electron deficit (cathode). Potential difference sets an electric field, which makes electrons move towards the positive terminal.
B. Electron Flow
Potential difference kickstarts the flow of electrons. During electron flow, the electrons coming from the negative terminal are repelled by the electrons bearing the same charge. Like charges tend to repel each other, and opposite charges attract each other. So when electrons flow out of a place with a surplus of electrons, they get attracted to a region with a lack of electrons or a more positive region. The electrons are attracted to the positive terminal as they flow out of the negative terminal. Similar to how the magnet's south pole is attracted to the north pole or an opposite pole of a magnet, electrons flow because itโs attracted to a region bearing an opposite side.
II. Components
Now that we know that potential difference triggers electron flow and electron flow occurs as a response to electron deficit lets examine the components of a simple circuit.
A. Power Source
A power source is anything that powers up the circuit. In a simple circuit, the battery serves as the power source. Power sources need to have an anode and cathode to set up an electric field that will power up a circuit. Even car batteries have positive and negative terminals because these are crucial elements that help the car start up.
B. Conductors
Think of conductors as the highway that allows electrical energy to pass through. When something is conductive, heat or electricity can move through it. Wires serve as the pathway for electrons. We often correlate live wire with being dangerous, and thatโs true. When a wire is exposed while connected to a power source, electron current continues unless it is detached from the power source.
C. Load
A load is anything that consumes energy. As electricity passes through the load, it encounters resistance, and as a response to this resistance, electrical energy is released. A load such as a light bulb uses this electrical energy and turns it into light and heat. Electrons continuously flow out of the load through the conductor and proceed to the positive end of the battery. A load may be a motor, a resistor, or anything that uses energy.
III. Conductance
Conductance describes how well a substance can support an electric current. Itโs a measure of how an object can conduct electricity. When something can conduct electricity well, it also has a good conductance. Earlier, we described conductance through a formula:
This formula shows that conductance (G) is inversely proportional to resistance (R). This means that when conductance increases, resistance decreases, and when resistanc,e is high, conductance is low. Ceramics have a high resistance, which also means ,that they have a low cothey havence and cannot conduct electricity.
Conductance is the reciprocal of resistance and is measured in Siemens (S). It is known as the ability to conduct electricity. Conversely, resistance tells us how well an object opposes electricity and is measured in ohms (ฮฉ). The next articleโll explore resistance and how it relates to voltage and current.IV. Conclusion
A circuit tells us how electricity works. A simple circuit has a power source that serves as the source of electrons. The power source must be connected to a conductor, which serves as the pathway for the electrons to flow. As electrons flow, they go through a load, which is a device that resists electron flow. This resistance results in electrical energy, which a load may use to fulfill the circuitโs purpose. Electrons will continuously move out of the load through a conductor until it reaches the battery's positive terminal. Conductance shows how well a material can carry electrical current. On the other hand, resistance tells us how well a material resists electrical current. Both values are inversely proportional, which means that when something has a high conductance, it also has a low resistance, and vice versa.
V. Key Terms
- Anode - negative terminal of the battery which loses electrons (oxidation)
- Cathode - positive terminal of the battery which gains electrons (reduction)
- Conductance - the ability to carry current
- Potential difference - the driving force of electron flow
- Resistance - the ability to resist the current
VI. Practice Questions
Sample Practice Question 1
Multiple sclerosis is a disease that affects the myelin sheath, disrupting the transmission of signals among nerves. One role of the myelin sheath is to prevent current from leaking out, which speeds up signal transmission. In a healthy nerve cell, how does the myelin sheath help allow signals to move through nerves?
A. It serves as the conductor and carries the signals to other nerves.
B. It reduces the conductance, which in turn increases the resistance of nerve signals.
C. It reduces the resistance, increasing the conductance of nerve signals.
D. It increases the resistance and the conductance, which allows signals to move through nerves.
Ans. C
Sample Practice Question 2
Which statement is not an accurate description of how a circuit works?
A. Electrons move from the negative terminal to the positive terminal.
B. Electrons move across a load that uses up the electrons.
C. The load uses electrical energy to produce light and heat.
D. From the load, electrons proceed to move towards the positive terminal.
Ans. B
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