Parallel Circuits

Parallel Circuits are very useful and are found in use in homes, cars, and street lights. The advantage of a parallel electrical circuit is that each fixture received electricity through its own unique circuit. In a house, for example, if one light bulb blows, electricity will still flow to all the other lights. This wouldn't happen if all the bulbs were in a single circuit.

The basic electricity formula, Ohms Law states that the current V (Volts) =  I (Current) x R (Resistance) . In parallel circuits, the voltage acting on each individual component of the circuit is the same; however, the total current and resistance is calculated differently. The formula for the current is I = I(1) +I(2) +I(3) . The resistance, on the other hand, is calculated as R = 1/R(1) + 1/R(2) + 1/(R(3)

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How Do Fuses Work?

Fuses have been in operation for a longtime, and their job is to prevent circuits from overloading. When exposed to a current above permitted levels, the fuse will "blow" and break the circuit. The central part of the fuse is the delicate melt wire, which is in line with the live circuit and which carries the current, yet burns up if the flow exceeds a certain level, thus breaking the circuit.

Fuses are very sensitive to rapid increases in current as occurs with a short circuit. With smaller increase in the current such as occurs in circuits attached to too many appliances, e.g.,  an air conditioner and appliances in the summer or a heater and appliances in the winter, the increase of current is smaller and it doesn't rapidly blow the fuse. To detect these current changes modern circuits have circuit breakers, overload relays and MCBs. These devices respond rapidly to changes in current and quickly break the circuit. 

Read About Parallel Circuits in the Home 

What Makes Fuses Blow and or Circuit Breakers Trip?

When fuses repeatedly blow or circuit breakers trip, the householder is right to wonder what is causing the problem. Generally, there are one of four possibilities.

Fuses and circuit breakers are meant to regulate the amount of electrical current that flows through a given section of the home. A typical fuse may tolerate 30 amps of current. If a  fuse is attached to a circuit that is actively supplying more than 30 amps, sending current to say an air conditioner, radio, and lamp, then the fuse will blow and break the circuit. This prevents circuit overloading, which can lead to dangerous electrical fires. The fix for this problem is to move heavy electrical use items such as a hair dryer to a less overloaded circuit, so as to keep the electrical flow even throughout the house.

Short circuits are another cause of excessive electrical flow and blown fuses. The short circuit may be caused by a live wire touching another live wire or a neutral wire. When this occurs, too much electricity begins to flow in the circuit that is shorted, and again the fuse blows.  The location of the short circuit may be in the home wiring, in an electrical fixture, or in the fixed wiring system. To test it out, turn off all electrical appliances and wall lighting in the house. If the fuse or breaker cuts off then the short is in the home wiring. If not, turn on fixed electrical circuits one by one. If this doesn't trip the breaker or blow the fuse then plug in electrical appliances one by one When you add in the circuit that has the short the fuse will blow or the breaker will trip. The solution is for the homeowner or electrician to repair the faulty circuit.

Finally, a loose wire, can cause too much electrical flow as electricity is expended trying to jump the gap. The solution here is to locate the loose circuit.

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Electrical Panel (Fuse Box)

Electricity enters the home from the local distribution company. Electricity enters through the main switch. From the main switch, the current flows to the fuse pox or panel box from whence it is split into circuits that distribute the flow of electricity throughout the home.

In the fuse box, the flow of electricity to each individual circuit is protected by either a fuse or circuit breaker or both. Fuses and circuit breakers detect abnormal amounts of flow to a circuit, which may relate to short circuits or overloading. When either device detects abnormal flow it will either trip (circuit breaker) or blow(fuse).

 The circuit breaker can be manually reset once the problem causing the abnormal flow is resolved; however, fuses must be replaced.  There are two types in home use. "P" fuses are used for general circuits, and "D" fuses, or time delayed fuses are used for large appliances.

Homeowners can change fuses or, if knowledgeable, install new outlets; however, certain electrical repair work should be left to licensed electricians. This includes upgrades of the electrical power panel, repair of overheating plugs,  and repair of repeatedly tripping circuit breakers of blown fuses.

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