Voltage and electric energy

Volts and Short Circuits

Electricity can be measured in many ways. One of the measures is called volts. A volt is the amount of push a current has. A volt is the force of the current.

The current used in houses has a lot of push. That used for most electric

stoves has 220 volts. Most other house currents have about 115 volts.

Sometimes insulation on wires burns.

Sometimes it breaks. Someone touching the wire can get a bad shock.

[Name some ways you have gotten shocks.] A person might even be killed.

Such a bad place in a circuit is a short circuit. It is called this because the

electrons go across the wires. They take a short cut.

VOLTAGE AND ELECTRIC ENERGY

What causes shocks and sparks?

What is the name for the «push" that causes negative charges to move?

What are two kinds of electrostatic generators?

What's voltage?

One way to understand what voltage means is to think about what happens when something becomes charged. Suppose you shuffled your feet along a wool or nylon rug on a dry day. You would become negatively charged. If you touched another person or a doorknob, you would feel a shock. Your might even see a spark.

The shock and the spark are caused by negative charges moving between you and whatever you touch. But what caused the negative charges to move? They must have been given some kind of «push."

When you shuffle your feet on a rug, negative charges move from the rug to you. Work must be done in order to move each negative charge from the rug to you. You do the work by shuffling your feet.

In doing the work to move the negative charges from the rug to you, you use energy. Energy is the ability to do work. The energy you use goes to the negative charges. The negative charges, with the extra energy, are stored up on you. The amount of energy stored up is equal to the amount of work done in moving the negative charges onto you. This energy is the "push" that can cause negative charges to move. That "push" is sometimes called voltage.

* Would electric sparks from an object be more likely to happen on a dry or on a wet day? Why?

History of the volt

In 1800, as the result of a professional disagreement over the galvanic

response advocated by Luigi Galvani, Alessandro Volta developed the

so-called Voltaic pile, a forerunner of the battery, which produced a steady

electric current. Volta had determined that the most effective pair of dissimilar

metals to produce electricity is zinc and silver.

In the 1880s, the International Electrical Congress, now the International

Electrotechnical Commission, approved the volt as the unit for electromotive

force. At that time, the volt was defined as the potential difference across a

conductor when a current of one ampere dissipates one watt of power.

This SI unit is named after Alessandro Volta. As with every International

System of Units (SI) unit whose name is derived from the proper name of a

person, the first letter of its symbol is upper case (V). When an SI unit is

spelled out in English, it should always begin with a lower case letter (volt).

Дата добавления: 2015-07-24