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SACA Electrical Circuits Study Quizzes with 100%
Correct Solutions
Interpreting Series Power Flow All upstream or downstream of the output device must be closed for the electricity to flow. In most series circuits, the input devices are also places upstream from the output device so they can also be placed downstream. Output can also be place in series with each other but this is not often done because the power decreases as the current flows through each output. Battery Applications A common source of DC current is a battery. A battery stores electricity in chemical form and converts it to electricity when a closed circuit is formed between its two terminals. Electricity The flow of electrons in a conductor. Electrons are very small, negatively charged particles that exist in every kind of matter. Electricity is a form of energy which is described by current and voltage. True Current The flow rate of electrons through the conductor. Voltage The amount of force required to move the electrons through the conductor. The unit of measure of current is Amperes (A), or Amps True The unit of measure of voltage is Volts (V)
True Increasing either current or volage increases the electrical energy True Electricity is used for a wide range of applications including:
- Lighting
- Heating/cooling
- Machine motion (electric motor)
- Communications (televisions, radios, computers, etc.) What are the basic components of an electrical circuit?
- Power Supply
- Input Device
- Output Device
- Conductor Closed Circuit An electrical circuit operates when the circuit is closed. A circuit is said to be closed if there is a complete path for current to flow between the positive and negative terminal. Open Circuit An electrical circuit stops operation when the circuit is opened. A circuit is open when the path is broken so electricity cannot flow. Circuit Switch A simple method for opening and closing a circuit is to use a switch. When the switch is closed, the circuit is closed and electricity flows. When the switch is open, the circuit is also open. Load Resistance
Direct Current (DC) DC electricity flows in only one direction. Using the conventional theory of current flow, the power supply creates flow from the highest potential (positive terminal) to the lowest potential (negative terminal). Alternating Current (AC) AC flows alternately in one direction and then in the other (cycles). The power supply creates the alternating current by pushing the electron flow in one direction for half the cycle and then in the other direction for the second half of the cycle. DC Power Supply Applications Another source of DC current is a DC power supply, which converts AC current from your wall outlet into a DC current. Personal computers use DC current sourced from a DC power supply. AC Power Applications AC electricity powers more devices than DC because it is more efficient to transport over long distances including from the power plant to the point of use. Power Supplies Used in electrical systems to modify the power supplied from the power company (e.g. from the wall socket) to a form that is needed for application. Power supplies are often designed to provide either a constant current or constant voltage. This is called regulation. Constant Current Supply A constant current supply provides the same current level regardless of the demand placed on it by the load. However, voltage varies according to the size of the load. The applications of a constant current supply are limited. They are most often used to supply a
specific current in process control circuits, where a constant current level is critical to the operation. Constant Voltage Power Supplies Constant voltage power supplies are more widely used. They maintain a constant voltage output, regardless of the load. Constant voltage power supplies come in various forms and can produce AC or DC voltage. Sometimes they even produce both. Batteries One type of constant voltage DC power supply is a battery. A battery depends on a chemical reaction to produce electricity. Other types of constant voltage power supplies require an external AC power source. Other Power Supply Functions In addition to regulating voltage or current, power supplies also provide other functions. Power supplies include circuitry to remove unwanted variations from the electricity, so it has a smooth output voltage or current. Many power supplies are also equipped with protective devices that prevent an overload. Two examples are a fuse and a circuit breaker. A basic constant voltage power supply consists of these basic components:
- AC Power Cord
- Voltage Display
- On/Off Switch
- Voltage Adjustment
- Positive and Negative Output Terminals
- Circuit Breaker
Operator The component that activates the switch. It causes the contact bar to switch between closed and open states. What are the 2 basic components of switches? An operator and one or more sets of contacts. Switches are classified according to the type of operator and contacts they have. Contacts The part of a switch that allows electricity to pass through. A set of contacts consists of two metal contact points with wiring terminals and a contact bar that connects the two points. Manually Operated Switches Knife Switch Pushbutton Switch Selector Switch Knife Switch Applications Often used in applications where a visual confirmation of the switch's state is important. A common application is the main disconnect switch for incoming power to a large machine. Selector Switch Often used to change machine mode, from automatic to manual or from forward to reverse. Pushbutton Switch A type of switch that activates by pressing a button on the switch. It consists of a pushbutton- type operator and one or more sets of contact.s Pushing the operator causes the contacts to be opened or closed depending on the default state. Momentary Switch
Switches with a spring return NO & NC Contact Types Pushbutton switches can have one of two types of contacts: Normally Open (NO) and Normally Closed (NC). What are the most common pushbutton operator colors? Green Red Black Yellow What are 5 basic electrical output devices? Lamps Resistors Buzzers Solenoids Motors Lamp When current flows through the element of a lap, visible light is generated. Resistor A resistor is made of a material that does not allow current to easily flow through it. The most common material used to make resistors is carbon. Resistors come in a wide range of values. Buzzer When electricity is applied to a buzzer, it causes a vibration to occur inside the buzzer's housing. The vibration is what causes the buzzing noise. Solenoid
Motor Regulation The function of a power supply that provides either a constant voltage or constant current. The Conventional Theory of Current Flow States that current flows form the positive terminal of the power supply to the negative terminal. Why do power supplies frequently have fuses or circuit breakers? To prevent overloads. A selector switch that returns to its original position when the knob is released is said to have: Momentary Action
