Recently one of our daughters, Jamie, was in a state of distress when, with her hair still wet, her electric blow dryer ceased operating.

With blow dryer in one hand, a damp towel in the other and dripping hair in her wake, she ran down the hall in search of an answer to her dilemma.

We gave the dryer a once-over and determined that the housing appeared to be all right –the switch was operating properly and the electrical cord and plug appeared to be fine. Confident that the dryer presented no imminent danger, we plugged it into another outlet. The device immediately produced its familiar whine along with an ample supply of hot air. Jamie seemed perplexed.

We unplugged the blow dryer, returned to her bathroom, plugged it into the outlet beside her sink, switched it on. Nothing. An inquisitive 11-year-old, Jamie couldn't understand why her blow dryer worked when plugged into an outlet across the house, but not in the outlet in her bathroom.

Since the blow dryer seemed not to be the culprit, we turned our attention to the outlet in her bathroom and tested it for power. We used an inexpensive two-pronged voltage tester that consists of two short lengths of insulated wire with exposed metal terminals at the ends, and a small light bulb at the opposite end. The test is simple. The terminals are plugged into the outlet, one in each of the two slots. When the bulb lights, power is present. No light, no power. Our test revealed that the outlet was indeed not "hot" –meaning it had no power.

This series of events led to a discussion about basic home electrical –Electricity 101, if you will. A home's electrical system, we explained, is divided into circuits that branch out to bring electricity to various spaces throughout a home. A circuit can consist of a single outlet or several outlets that are joined together by wires concealed in walls and the attic. All electrical circuits, we continued, terminate at a subpanel –more commonly known as a breaker box or, with older homes, a fuse box. Depending upon the size and age of a home, more than one subpanel can exist. Still, in other cases, the subpanel and the main service (where the main power comes into the home and the meter is generally located) are one in the same.

In our case, the subpanel is located in our laundry room. Jamie still wasn't clear about what this had to do with why her blow dryer wasn't working. We assured her that we were working our way toward the answer.

We opened the subpanel door to expose a neat arrangement of black switches called circuit breakers. We explained that each of the breakers in the panel controlled power to the various electrical circuits throughout our house. Among the group of neatly arranged black switches in the panel was one errant switch. We compared the number on the breaker with the corresponding number on the legend located on the inside face of the panel door and discovered that it was the breaker that controlled the power to the electrical outlet in her bathroom.

We moved the breaker to the off position and then flipped it to the on position and returned to her bathroom to see if the blow dryer would now function. As we expected, and to Jamie's delight, her oultet was back in business. However, by this time, Jamie's hair was nearly dry and her concern turned from her dryer problems to why the breaker had "tripped" in the first place.

We explained that breakers and their predecessors, fuses, are safety devices that prevent electrical wire from overheating, a condition that could result in an electrical fire. Although a breaker can trip for many reasons, it is usually caused either by a short or an overloaded circuit. A circuit becomes overloaded when the power draw is greater than the circuit is designed to supply. The breaker, the wire and the outlet are sized to meet the specific power demand of a given circuit.

When this limit is exceeded, the breaker trips, preventing the wire from overheating and possibly causing a fire.

So, Jamie wanted to know what caused the breaker that supplies power to the outlet in her bathroom to trip. Just as we were preparing to further investigate, her older brother Chris arrived on the scene to report that his blow dryer stopped working about the same time as Jamie's. We then discovered that the siblings' outlets were on the same electrical circuit; when they powered up their blow dryers at the same time, the process drew more wattage than the circuit was rated to carry and, thus, the circuit breaker tripped.

If breakers are constantly tripping and you find yourself flipping breakers or replacing fuses often, chances are you are overloading a circuit. Consider splitting the load by plugging devices into different circuits. Recurring electrical problems should be investigated by a qualified electrician.