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Background Information for Electricity
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Below you will find some commonly asked questions about electricity. You may also want to explore the other topics relating to our school program «Electricity Workshop».
- What is electricity?
- Who discovered electricity?
- What is static electricity?
- What are the laws of electrostatics?
- Why do two balloons that have just been rubbed with a wool cloth, move away from each other?
- What is current?
- What is current electricity?
- What is the difference between alternating and direct current?
- What is a conductor?
- What is an insulator?
- What is resistance?
- What is a magnetic field?
- What is electromagnetism?
- How are magnetism and electricity connected?
- What is an electrical circuit?
- How does a fuse work?
- Why does your hair stand on end at the Van de Graaff generator?
What is electricity?
It is a form of energy, evident from the fact that it runs machinery and can be transformed into other types of energy such as light and heat.
It is invisible. During an electrical storm, we do not see electricity. We observe the air being ionized when the electricity travels through it.
Electricity is created when particles become charged. Some are negatively charged (electrons), some are positively charged(protons). These opposite charges attract; whereas particles with similar charges repel each other.
The nucleus of the atom contains protons (positively charged) and neutrons (no charge) around which electrons (negatively charged) whirl. An electron is two thousand times smaller in mass than a proton but its electrical charge is equal to that of a proton. Electrons of many elements, particularly metals, are easily knocked off from their parent atoms and can wander freely between atoms. If a state of unbalanced charges exists, a necessary condition to create an electric current also exists. However, the flow of electric current cannot take place until the circuit is completed. When a battery or other electrical source is attached to a wire, which is connected to some form of resistance, (a light, a bell, a motor, etc.), and a circuit is completed back to the source or to ground, free electrons are released into the wire, creating an electrical potential or voltage. The electrons bounce against other electrons in the wire which are repelled because they have the same electrical charge. They go on bouncing against other free electrons down the wire, causing a flow of electrons - an electrical current. Provided there is somewhere for the electrons to go, such as a lamp or a motor, where the energy is converted to another form of energy, the electrons flow out the far end.
Who discovered electricity?
The Greeks had some idea of electricity.
In the 18th century Franklin and other Europeans knew a great deal about it. Early in the century, Alessandro Volta invented the first source of continuous electric current - the battery. Later, Hans Christian Oersted discovered that an electric current produced magnetism.
But it was Michael Faraday who described the nature of the phenomena. In his electromagnetic induction theory he stated that an electric current flows in a conductor if that conductor is in a moving magnetic field and is part of a circuit.
What is static electricity?
Static electricity is electricity at rest. It is produced by friction, by rubbing. All matter contains positively charged particles called protons and negatively charged particles called electrons. In an uncharged atom, the protons and electrons balance each other and the atom is neutral. If this neutral atom loses an electron, because it has an excess of protons, it is said to be positively charged. If the neutral atom gains an electron, it is said to be negatively charged.
Rubbing can tear electrons loose from certain atoms. Some substances, because of the character of their atoms, tend to lose electrons and become positively charged; other substances gain electrons easily and become negatively charged.
What are the laws of electrostatics?
Unlike charges attract; like charges repel.
Why do two balloons that have just been rubbed with a wool cloth, move away from each other?
When a balloon is rubbed with a wool cloth, the wool loses some of its electrons. Because the wool has more protons than electrons, we say that it is positively charged. The balloon gains electrons from the cloth and is said to be negatively charged. If the negatively charged balloon is brought close to the positively charged cloth, it attracts the wool. If two negatively charged balloons are brought close together, the like charges repel and the balloons move away from each other.
What is current?
Current is the rate of flow of electrons. It is produced by electrons "on the move", and it is measured in amperes.Unlike static electricity, current electricity must flow through a conducter, usually copper wire. Household current is usually no more than 30 amps.
What is current electricity?
Current electricity is a stream of electrons flowing through a conductor. There are different sources of current electricity including the chemical reactions taking place in a battery and the application of pressure on quartz crystals. However, the most significant source is the generator. A simple magneto, or generator, produces electricity when a coil of copper turns inside a magnetic field. In a power plant, electromagnets spinning inside an armature of many coils of copper wire generate vast quantities of current electricity.
What is the difference between alternating and direct current?
A battery produces direct current (DC).The electrons are set in motion by a chemical reaction in a battery and flow only one way. A generator, on the other hand, produces alternating current (AC), because the wire coil core is influenced alternately by the North and South Poles of the magnets. The current is therefore constantly changing direction.
What is a conductor?
Electricity flows more easily through some materials than through others. Conductors let electricity flow through them easily. Most metals are good conductors, so they are used to make wires for carrying electrical current.
What is an insulator?
Insulators, such as glass, stop the flow of electricity. Most plastics are insulators. Wires carrying electricity are covered in plastic to prevent electric shocks.
What is resistance?
Resistance is the property of a substance that prevents the flow of electrons, and it is measured in units called ohms. Materials with high resistance, like plexiglass and rubber, are called insulators, since they do not easily allow electricity to pass through them.
Materials with low resistance, such as copper and aluminum are called conductors, because they let electricity flow through them easily. Electricity passing through a material will heat the material relative to the resistance of that material.
What is a magnetic field?
When an electric current flows through a wire, it produces a magnetic field around the wire. The greater the current, the stronger the magnetic field. By coiling up the wire many times, the magnetic field produced can be made even stronger.
The Earth is like a gigantic magnet with lines of magnetic force running from the North Pole to the South Pole. A compass needle lines up with the Earth's magnetic field, pointing towards magnetic North. Like the Earth, all magnets have a North and South Pole and are surrounded by invisible "lines of magnetic force".
What is electromagnetism?
Michael Faraday discovered that a magnetic field can generate an electric current. This principle of induction can be effectively demonstrated by moving a bar magnet in and out of a coil of copper wire attached to a meter, or by using a magneto. A magneto is an assembly of magnets enclosing a copper coil. When the copper coil is turned in the magnetic fields of the magnets, electricity is produced.
How are magnetism and electricity connected?
In a generator or magneto, magnetism can induce electricity; in an electromagnet, electricity induces magnetism.
Combining electricity with rotating magnets makes an electric motor.
What is an electrical circuit?
A circuit connects electrical components in a closed path or loop. It includes a source of power, one or more on and off switches, interconnecting wires and an electrical appliance such as a bell or a lightbulb.
How does a fuse work?
A fuse is connected directly into an electrical circuit. If the electric current surges to a dangerous level, the metal in the fuse melts and the circuit is broken, preventing overheated wires in the walls of the house from starting a fire.Never substitute a fuse of greater capacity than that specified for a particular circuit. If the fuse has the ability to carry more current than originally designed, the wires will heat up before the fuse melts, and this could start a fire.
Why does your hair stand on end at the Van de Graaff generator in the Museum?
The Museum's Van de Graaff generator removes electrons from the large globe, giving it a high positive charge. If you stand on an insulated plate and touch this globe, all parts of your body become positively charged, including your hair. Since like charges repel, every hair on your head is now trying to get away from every other hair. The best way is to stand straight up. Result - flyaway hairdo!
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