The same voltage is applied across each branch. If the load resistance in each branch is the same, the current in each branch will be the same. If the load resistance in each branch is different, the current in each branch will be different. The components of a parallel circuit are connected side by side so the current flow has a choice of paths in the circuit. If one branch is broken, current will continue flowing to the other branches. In the parallel circuit below, two or more resistances R1, R2, etc.
A series-parallel circuit has some components in series and others in parallel. The power source and control or protection devices are usually in series; the loads are usually in parallel. If the series portion is broken, current stops flowing in the entire circuit. If a parallel branch is broken, current continues flowing in the series portion and the remaining branches.
Interior dash lights are a good example of a resistance and lamps connected in a series-parallel circuit. In this example, by adjusting the rheostat, you can increase or decrease the brilliance of the lights. Electrical circuit issues are usually caused by a failed component or low or high resistance in a circuit.
Low resistance in a circuit may generally be caused by a shorted component, or a short to ground, and will generally cause a fuse, fusible link or circuit breaker to blow. High resistance in a circuit can be caused by corrosion or an open in the source side or the ground side of a circuit.
Circuit protection devices are used to protect wires and connectors from being damaged by excess current flow caused by either an over current or short-circuit. Fuses, fuse elements, fusible links, and circuit breakers are used as circuit protection devices.
Circuit protection devices are available in a variety of types, shapes, and specific current ratings. A fuse is the most common type of overcurrent protection device. A fuse is placed in an electrical circuit and receives the same electric supply as the protected circuit. A short or ground condition allows current to flow to ground before it reaches the load.
This opens or interrupts the circuit and preventing wires and connectors and electronic components of the circuit from being damaged by the over current. The size of the metal fuse element or fuse link determines its rating. A fuse should normally be selected with a rating just over the normal operating current amperage which can be used at any voltage below the fuse voltage rating.
If the new fuse blows too, then there is something wrong with the circuit. Check the wiring to the components that run off the blown fuse.
Look for bad connections, cuts, breaks or shorts. Fuses have different time-current load characteristics for finite operating time in use, and for the speed at which a fuse element blows in response to an overcurrent condition.
Fuses are located throughout the entire vehicle. Common locations include the engine compartment, under the dashboard behind the left or right kick panels, or under the IPDM. Fuses are usually grouped together and are often mixed in with other components like relays, circuit breakers, and fuse elements.
Fuses are classified into basic categories: blade type fuses and old-glass style cartridge fuses. Several variations of each are used.
The blade fuse and fuse element are by far the most commonly used today. Blade type fuses have a plastic body and two prongs that fit into sockets and can be mounted in fuse blocks, in-line fuse holders, or fuse clips. Three different types of blade fuses exist; the Maxi Fuse, the Standard Auto fuse, and the Mini fuse. The blade type fuse is a compact design with a metal element and transparent insulating housing which is color-coded for each current rating.
Standard Auto shown below; however construction of both the Mini and Maxi fuses are the same. Fuse amperage color ratings for both the Mini and standard Auto fuses are identical. However, the amperage color ratings of maxi fuses use a different color coding scheme. Fusible links are divided into two categories: the fuse element cartridge and the fusible link. The construction and function of fusible links and fuse elements are similar to that of a fuse.
The main difference is that the fusible link and fuse element are used to protect higher amperage electrical circuits, generally circuits 30 amps or more. As with fuses, once a fusible link or fuse element blows out, it must be replaced with a new one. Fusible links protect circuits between the battery and the fuse block. Fusible links are short pieces of a smaller diameter wire designed to melt during an over current condition.
A fusible link is usually four 4 wire sizes smaller than the circuit that it is protecting. The insulation of a fusible link is a special nonflammable material. This allows the wire to melt, but the insulation to remain intact for safety. Some fusible links have a tag at one end that indicates its rating. Many manufacturers have replaced fusible links with fuse elements or Maxi fuses.
Fuse elements, a cartridge type fusible link, are also known as a Pacific fuses. The element has the terminal and fusing portion as a unit. Fuse elements have all but replaced the fusible link. They consist of a housing that contains both the terminal and fuse.
Fuse element cartridges are color coded for each current amperage. Although fuse elements are available in two physical sizes and are either plug in or bolt on design, the plug-in type is the most popular.
Construction of the fuse element is quite simple. A colored plastic housing contains the fusing portion element which can be viewed through a clear top. Fuse ratings are also stamped on the case. Fuse amperage color ratings are shown below. The fusing portion of the fuse element is visible through a clear window.
The amperage ratings are also listed on the fuse element. Circuit breakers are used in place of fuses for the protection of complicated power circuits such as the power windows, sunroofs and heater circuits.
Three types of circuit breakers exists: The manual reset type - mechanical, the automatic resetting type - mechanical, and the automatically reset solid state type - PTC. A circuit breaker basically consists of a bimetal strip connected to two terminals and to a contact in between.
Manual circuit breaker when tripped current flow beyond its rating will open and must be reset manually. The circuit breaker contains a metal strip made of two different metals bonded together called a bimetal strip. This strip is in the shape of a disc and is concaved downward. When heat from the excessive current is higher than the circuit breaker current rating, the two metals change shape unevenly. The strip bends or warps upwards and the contacts open to stop current flow.
The circuit breaker can be reset after it is tripped. When a circuit breaker is opened by an over-current condition, the circuit breaker requires reset.
To do so, insert a small rod paper clip to reset the bimetal plate as shown. This type of circuit breaker is used to protect high current circuits, such as power door locks, power windows, air conditioning, etc. The automatically resetting circuit breaker contains a bimetal strip. The bimetal strip will overheat and open from the excess current by an overcurrent condition and is automatically reset when the temperature of the bimetal strip cools.
A cycling circuit breaker contains a metal strip made of two different metals bonded together called a bimetal strip. When heat from the excessive current is higher than the circuit breaker current rating the two metals change shape unevenly.
The strip bends upwards and a set of contacts open to stop current flow. With no current flowing the bimetal strip cools and returns to its normal shape, closing the contacts, and resuming the current flow.
A Polymer PTC is a special type of circuit breaker called a thermistor or thermal resistor. A PTC thermistor increases resistance as its temperature is increased. PTCs, which are made from a conductive polymer, are a solid state device, which means they have no moving parts. PTCs are commonly used to protect power window and power door lock circuits. In its normal state, the material in a polymer PTC is in the form of a dense crystal, with many carbon particles packed together. The carbon particles provide conductive pathways for current flow.
This resistance is low. When the material is heated from excessive current, the polymer expands, pulling the carbon chains apart.
It resets only when voltage is removed and the polymer cools. PTCs are used to protect power window and power door lock circuits. Control devices include a variety of switches, relays, and solenoids. Electronic control devices include capacitors, diodes, and switching transistors. Switching transistors act as a electronically-controlled switch or relay.
The advantage of a transistor is its speed in opening and closing a circuit. Control devices are needed to start, stop, or redirect current flow in an electrical circuit. A switch is just a connection in the circuit that can be opened or closed. Most switches require physical movement for operation while relays and solenoids are operated with electromagnetism.
A switch is the most common circuit control device. A switch controls current flow into a circuit. The power supply can be the mains or the wall outlet, or a generator or alternator, or a battery.
The load can be a motor, light, heater, or a combination of these, but it must be capable of handling the power supplied by the source. If the power does not match the load, it can either burn out the load or not supply enough power to operate it properly. The conductor wires also need to be a sufficient size to carry the current from the source to the load and back again.
A switch is used to conveniently permit the current to flow through the load, or to turn off the current. This allows control of the circuit without interrupting the operation of the power source. The work is a variation on a resistance in the circuit. Because we can pick any time frame we want, it doesn't really matter in this question. The light bulb at the end of the flashlight is the device into which the current flows.
Current flows through a very tiny filament which heats up to a very high temperature because of the electrical resistance.
As a result, the filament glows brightly. The circuit is finally completed by a strip of metal that goes down the side barrel of the flashlight. There is also a coil of wire at one end of the flashlight and at the other end there are the contact points for the battery as well as the other strip of wire that together complete the circuit.
Flashlights and most other electrical appliances also have a switch. A switch is merely a device that helps to break the continuous loop of the conducting material. When the switch is open, there is no flow of current but when the switch is closed, there is a flow. Basically, all circuits work like this. A fuse or a circuit breaker is used to prevent major fires due to overloads. A fuse is designed to burn up if the current gets too high.
Learn more about the first law of thermodynamics. There are two types of circuits found in homes and other common devices; namely series circuits and parallel circuits.
Series Circuits — Series circuits consists of several devices, each of them linked up one after another after another in just a single large loop. Though,different devices have different voltages across them, the same current flows through every device in the series circuit. If any one of the devices in a series circuit is broken, the whole circuit fails.
For instance, if there are three light bulbs connected in a series, in just one loop of wire connected to a battery. If one light bulb is unscrewed, the whole circuit fails. Parallel Circuits —In parallel circuits, different devices are arranged so that a single source supplies voltage to separate loops of wire. The voltage in every device across the circuit is exactly the same, but in general different devices are going to see different currents.
In this case, each device is going to work even if the other ones fail. For instance, if two light bulbs are linked up in parallel and one is unscrewed, the other one will work. This is a transcript from the video series The Joy of Science. Watch it now, on Wondrium. Learn more about entropy.
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