Expert Verified Answer When resistors are connected in series, their total resistance is less than that of the smallest resistor. Fuse circuits are used to avoid overloading. In most cases, a fuse or circuit breaker used in a circuit is connected in parallel. The purpose of this arrangement is to protect other components on the line if one device fails. For example, if you were using two lamps and both bulbs failed, the remaining lamp would still be able to supply light because its circuit is separate from the first lamp's circuit. If both lamps' circuits were tied together, either bulb could cause the entire set to fail.
In many cases, such as with motors, heaters, and appliances that use lots of current, the best way to protect other equipment on the line is to connect each device in parallel. This will allow all the circuits to open if any single component fails.
There are several types of fuses: auto-reset, magnetic, electric, and carbon arc. Each type has various advantages and disadvantages. Which type you should use depends on what kind of protection you need and how much money you're willing to spend.
In a parallel circuit, the overall resistance is smaller than the sum of the individual resistances. Each parallel resistor receives the same voltage from the source (voltage is constant in a parallel circuit). As such, they all experience the same current through them, which means that they all heat up to the same temperature. The only difference between them is their resistance, so if you know one resistance value, you know them all.
The current through each resistor is equal, so the power consumed by each resistor is also equal. Since power is rate times voltage, this means that the rate at which each resistor consumes energy is the same.
As long as the voltage remains the same, the current will always be the same too. This means that regardless of what type of resistor you have in your circuit, it will always take the same amount of time to heat up.
When resistors are linked in parallel, more current flows from the source than would flow if they were connected separately, resulting in a lower overall resistance. Each parallel resistor receives the same full voltage from the source but distributes the whole current amongst itself. The value of the combined total is equal to the sum of the values of the individual components.
In practice, resistors of the same value will be used in parallel to reduce the current consumed by a load. This is particularly important for batteries which must be recharged after use. A low-value resistor is used in conjunction with a high-value resistor to divide down the current drawn from the battery without reducing it too much. The low-value resistor then heats up less, so its temperature does not have to be as closely regulated.
Resistors can also be used in series to increase the load current rating of an electrical circuit. For example, two 1 kΩ resistors in series provide 2 kΩ of resistance, enough to supply twice the current through an LED compared to a single 1 kΩ resistor.
Finally, resistors can be used in combination with other components to create circuits such as oscillators, frequency dividers, and timers. These devices require precise timing to work properly, so resistors are usually chosen that have stable values under varying conditions of temperature and power supply voltage.
If fuses and circuit breakers are factory constructed in parallel and classified as a unit, they can be joined in parallel. Individual fuses, circuit breakers, or combinations thereof must never be linked in parallel. If this connection is made, either the current will flow through all of the devices, regardless of whether any open circuits exist, or none of them will work at all.
The link shows how two groups of fuses can be field-wired together in parallel. In this case, each group contains equal numbers of AC 120-volt fuses and 240-volt fuses. All the fuses in both groups will blow if the power goes out.
Field-wiring in parallel is useful when you have several circuits that require different voltage thresholds for activation. For example, if your house was destroyed by fire but not by water, you would still need to have your electricity turned back on. Field-wiring allows you to connect all the low-voltage cables in parallel while keeping the high-voltage cable isolated from these other cables.
You should always connect electrical components in parallel whenever possible. This saves energy and reduces the risk of one component failing when needed most.
Paralleling as stated is a violation of the National Electric Code, article 240.8: Paralleling Fuses or Circuit Breakers. However, if the individual devices are accessible from outside the enclosure, they must be accessed in a way that will not expose live parts of the system to danger. This means that you cannot access both units from inside their common housing.
The reason for this rule is that if one device fails open, it could cause another device with which it is paralleled to also trip, even though it was not affected by the initial failure. For example, if you were to access both units' fuse boxes from inside a house, and one box had its lid left open, you would be violating this rule.
However, if both units are inside separate enclosures and there is no way for one to affect the other through external exposure, then they can be paralleled without problem. For example, if one fuse panel is located in a basement room with no access from the outside, it can be paired with any number of other fuse panels located in other rooms with no problem. The same thing goes for circuit breakers- if they can't see or reach each other they can be placed anywhere in parallel.
Parallel circuits are those in which the charges leaving the potential source can take multiple pathways back to the source. Each resistor (light bulb) in this parallel circuit is connected across the battery as if the other two resistors were not there. If any one of the light bulbs goes out, its connection to the battery will be broken, but the remaining light bulbs still provide a complete circuit that cannot cause overcurrent unless all the bulbs are out.
In general, anything that is intended to be connected in parallel with other like items must have enough contact points for all the items being paralleled. For example, six contacts or more are needed for six parallel-connected light bulbs of ordinary size; three contacts or less are sufficient for small bulbs of special design. The number of contacts required depends on how many different ways current can be routed through the group. If each bulb could handle only one current path, then at least two contacts are needed for each item being paralleled.
Contacts that connect wires in wiring diagrams or list sheets to individual components are called "through-hole connectors." Wires that do not require through-holes are called "surface-mount connections."
A common mistake is to assume that any two adjacent pins on a connector are suitable for making a surface-mount connection. This is not so; they must be chosen carefully to prevent shorting between adjacent pins.