Molly Ayala
Chapter 9 of the Electricity and Circuits guide provides an overview of how to turn electricity on and off. It covers the basics of electric circuits, including the materials that conduct electricity and those that act as insulators. The chapter also delves into the function of switches in a circuit, which is to control the flow of electricity to an appliance. Additionally, it discusses the safety considerations when dealing with electrical issues at home, such as locating the electrical service panel or breaker box, identifying the relevant circuit breakers, and safely turning them off to prevent electrical shocks and fires.
| Characteristics | Values |
|---|---|
| Materials that allow current to pass through them | Conductors e.g. Copper, Aluminium |
| Materials that do not allow current to pass through them | Insulators e.g. Plastic, Wood |
| Example of a device with two terminals | Bulb |
| Definition of electric current | The rate of flow of electric charge through a conductor per unit time |
| Example of electricity generation | Solar cells |
| Properties of solar cells | 1. Generally non-rechargeable 2. Expensive 3. Not long-lasting |
| Definition of a battery | The positive terminal of one cell is kept in contact with the negative terminal of another cell |
| Function of a switch | To make or break an electric circuit |
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What You'll Learn
The function of a switch
An electric switch is a component that can connect or disconnect the conducting path in an electrical circuit, thereby turning an electric current on or off. It does so by either permitting or deflecting electrons to pass through a circuit. In other words, a switch can make or break an electric circuit.
The most familiar form of a switch is a manually operated electromechanical device with one or more sets of electrical contacts, which are connected to external circuits. Each set of contacts can be in one of two states: "closed", meaning the contacts are touching and electricity can flow between them; or "open", meaning the contacts are separated and the switch is non-conducting. The mechanism actuating the transition between these two states is usually either an ""alternate action" (flip the switch for continuous "on" or "off") or "momentary" (push for "on" and release for "off") type. A switch may be directly manipulated by a human as a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch.
Switches are also used to regulate or command decisions about when and in what manner a particular device will operate. For example, a smart electrical switch can be integrated into home automation, allowing users to control lights, fans, and other appliances through applications or voice commands. Dimmer switches enable individuals to change the light illumination level by regulating the voltage feeding the light bulb.
Safety is another important function of an electric switch. Switches enable people to cut off electrical appliances and devices from the power source to minimize the outbreak of electrical fires, short-circuit occurrences, or overloads. Switches may also be used to isolate electric power from a system, providing a visible point of isolation that can be padlocked to prevent accidental operation of a machine during maintenance or to prevent electric shock.
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Conductors and insulators
Conductors are materials that allow electrons to flow freely from atom to atom and molecule to molecule. This free movement of electrons means that a charge is quickly distributed across the entire surface of the object. If a charged conductor touches another object, it can transfer its charge. Metals like silver, copper, and aluminium are conductors, as is carbon in the form of graphite, and the human body. The presence of "free electrons" in a substance makes it a conductor of electricity.
Insulators, on the other hand, do not allow electric charges to flow through them. Electrons and ions in insulators are bound in the structure and cannot move easily. Glass, rubber, plastic, paper, dry wood, cotton, and pure water are all examples of insulators.
Insulators are not useful for transferring charge, but they do serve a critical role in electrostatic experiments and demonstrations. Conductive objects are often mounted upon insulating objects, which prevents the charge from being transferred from the conductive object to its surroundings. Insulators are used in making switchboards and the handles of tools used by electricians, providing insulation and preventing accidental electric shocks.
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Electric circuits
A basic electric circuit consists of a switch, battery, and lamp. The switch controls the flow of electric charge, acting as a gatekeeper to turn the current on or off. The battery is the source of energy, providing the necessary voltage to power the circuit. The lamp is the device that uses the current, completing the circuit and allowing the flow of electrons.
On the other hand, alternating-current circuits, which are more common in household wiring, carry a current that pulsates back and forth many times per second. This type of circuit powers most of our everyday appliances, like lights and electric motors.
It's important to understand that any break in an electric circuit, no matter where it occurs, will prevent the flow of charge carriers or electrons. This discontinuity disrupts the continuous loop of conductive material, and the circuit is considered "broken". To restore the flow of current, the circuit must be repaired to re-establish a complete and unbroken path.
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Electric appliances
When it comes to electric appliances, there are several ways to reduce electricity usage and costs. Firstly, it is important to choose energy-efficient appliances. Modern appliances are generally more energy-efficient than older ones. When replacing an appliance, look for energy-efficient alternatives, such as those with an ENERGY STAR® rating, which indicates lower power consumption in standby mode. Additionally, appliances with a higher number of stars on their energy rating label are more efficient, reducing both energy consumption and costs.
Another way to reduce electricity usage is to unplug appliances when they are not in use. Even when turned off, appliances can still draw a small amount of electricity if they remain plugged in, a phenomenon known as “phantom power” or "standby power". This can add up to significant electricity usage and costs over time. To completely prevent this, unplug devices or use a power strip with on/off switches, allowing you to turn off multiple appliances at once.
Certain appliances, such as refrigerators, freezers, and alarm clocks, may need to remain plugged in at all times. In these cases, ensure that you purchase energy-efficient models and open them as infrequently as possible, as this can reduce power usage. For other appliances, such as dishwashers, consider using them only when they are full or opting for manual alternatives, like hand-washing dishes.
To identify which appliances are consuming the most power, consider using an electricity monitor. Plug an appliance into the monitor to measure its power consumption, cost of operation, and power usage over time. This can help you make informed decisions about which appliances to use sparingly or turn off when not in use.
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Electric current
The rate of flow of electric charge through a conductor per unit of time is defined as electric current. It is measured using a device called an ammeter and the common unit of measurement is the ampere, or amp for short. One ampere is defined as a flow of one coulomb of charge per second, or approximately 6.2 x 10^18 electrons per second.
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Frequently asked questions
A circuit breaker is a switch that automatically shuts off the electrical flow when it detects an overloaded or short circuit.
There are several instances when you might need to turn off a circuit breaker, including electrical maintenance, system overloads, and repairing or replacing major appliances.
First, locate the electrical service panel, which is usually located in a utility area. Then, flip the switch to the "off" position.
A switch is used to turn the current to an electrical appliance on or off.
