SPEED OF ELECTRICITY

Speed of electricity

Free electrons in a conductor material are pulled from one atom to another one and so on. By moving that extremely short distances in the case of being forced through electricity, the electricity itself develops a speed of around 320,000 km/h.

As the electrons are moving they temporarily rotate around each new centre. We already know an electron carries a negative charge of electricity and so the electron flow (current flow) is assumed to be from negative to positive.

Electron drift

The rate of drifting of the free electrons from atom to atom determines the amount of current. To create a drift of electrons through a circuit we must have an electrical pressure, the voltage. The more electrons the stronger the current.

That means i.e. in the case of a starter battery, the greater the concentration of electrons at a battery, the higher the pressure between the electrons and the greater that pressure is, the greater is the flow of electrons.

Volts, Amperes, Ohms, Watts

The pressure between the electrons, namely voltage, is measured in volts (V).

One unit of volt is the Potential Difference (P. D.) between two points of a conductor by a constant current flow of one ampere (1 A) when the power dissipated between these points is equal to one watt (1W).

The flow of electrons, the current, is measured in ampere (A).

One unit of ampere is that constant current (I) that (if maintained in two parallel rectilinear conductors of infinite length of negligible cross section and placed at a distance of one meter apart in vacuum) would produce between the (these) conductors a force equal to 2 × 10−7 Newton per meter length.

Opposing the flow of electrons is the resistance of the conductors measured in ohms (?).

One unit of electrical resistance (R) is the resistance between two points of a conductor if a constant

Potential Difference of one volt (1 V) applied between these points produces a current of one ampere (1A) and the conductor isn’t the source of an electromotive force.

Some materials offer a bigger resistance to the electron flow than others. For example the resistance of iron is higher than the resistance of copper, but the resistance of silver is less than the one of copper.

Also the length and the size of a wire are important facts to look for in that case.

The electric power (P) is the product of voltage (E) and current (I) and is measured in watt (W).

P = E × I; (P = U × I)

Electrical loads such as i. e. electric motors, coils and bulbs will consume power.

Ohm’s Law

The Ohm’s Law is the understanding of the mathematical relationship between voltage (E), current (I)

and resistance (R) in an electrical circuit. Each and every one affects the other one.

All that is the same and that means:

The Potential Difference (PD = voltage) in a conductor is under constant conditions equal to the current flow multiplied with resistance (oppose directed to the current) of the conductor.

The current through a conductor under constant conditions is proportional to the difference of potential across the conductor.

Types of electrical circuits:

We do know three general types of electrical circuits:

Series circuit; Parallel circuit; Series−parallel circuit. For all circuits there are a need for an electricity source (battery), electrical equipment (switch, bulb, etc.) and electrical conductors (wires) to connect the equipment with the source.

Series circuit: The current passes from the power source to each device in turn and then flows back to the other terminal of the source (only one path has the current). The amount of current will be the same in all

parts of the circuit.

Parts of a simple electrical circuit:

− source of electricity

− switch

− cable

− consumer

Parallel circuit: One terminal of each device is connected to a common conductor, which leads to one

terminal of the source. There is more than one path for the current to flow and therefore each and every

path has a separate amount of current flow depending on the equipment by forcing a weaker current flow or

stronger one.

Parts of a circuit:

− one source of electricity

− cable and eventually cable connectors

− the quantity and kind of switches and consumer depends on the kind of the circuit

Series−parallel

Series−parallel circuit: Such kinds of circuits have electrical devices connected in series and others connected in parallel. That means we do have more than one path for the current to flow.

Measuring resistance

To find the total resistance (RT) of a series circuit is to add the resistance of each device.

This means as well, when a number of resistance’s are connected together in series the current is the same in every part of the circuit.

In series the P. D. (Potential Difference) across each resistance is in general different. The overall P. D.

is equal to the sum of all P. D. across the individual resistances

In a parallel circuit we do have more than one path for the current flow. Therefore the total resistance of all the devices will be less than the resistance of any single device. Resistance is the ability of any wire or electrical component to oppose the flow of current.

Conductance is the reciprocal (opposite) of resistance.