Electricity Explained

Getting Down To Basics

By Bruce W. Maki

Current Flow and Ohm's Law

In the early days scientists discovered a link between electro-motive force and electron flow, in a given circuit or pathway. As the EMF was increased, the amount of electron flow increased proportionally.

Some circuits had more or less electron flow when attached to a given source of EMF. Scientists arrived at three basic concepts.

• Force - Some force was pushing or pulling the electrons to move in a circuit.
• Flow - Electrons would flow in a loop when there was a force pushing them.
• Resistance - The materials of the circuit would make it easier or harder for electrons to flow.

Over time, scientists named these three most important concepts in electrical science.

• Force is described as EMF or Voltage, measured in Volts.
• Flow of electrons is described as Current, measured in Amperes (often abbreviated as Amps)
• Resistance to flow is simply called electrical resistance, measured in Ohms.

The relationship between these three is utterly and totally critical in the understanding of electricity. It is described in Ohms Law, the fundamental physical law governing electricity.

Volts
---------------

Amps | Ohms

(Hint: cover up the term you are wanting to find, and the other terms will give the answer. The little vertical bar between Amps and Ohms means "multiplied by")

Volts = Amps X Ohms
Amps = Volts / Ohms
Ohms = Volts / Amps

This isn’t just scientific mumbo-jumbo. Everybody who wants to work on electric circuits NEEDS to fully understand this simple equation. If ninth graders can master this, SO CAN YOU !!!

Ohms Law tells us simple but crucial facts like:

• If the voltage is doubled on a given circuit, then the current flow (Amps) will double.
• If the current flow became doubled on a given circuit, but the applied voltage stayed the same, then the resistance must have been reduced to one-half of its previous level.
• If a circuit has a high but measurable resistance, and voltage is applied, then some current will flow. (Although the current would be very small.)
• If a circuit has infinite resistance, and voltage is applied, then no current will flow. (Air has infinite resistance, as do most insulators)
• If a circuit has a very low resistance (such as a piece of wire or a piece of metal) and voltage is applied, then a very large current will flow.
• If no voltage is applied, then no current will flow.

And One Of The Most Important Facts:

The human body has a medium level of resistance... unless the body becomes wet through rain or perspiration, which can drastically reduce the electrical resistance.

Contact with a high voltage (such as a live wire) will cause current to flow through your body unless your body is completely insulated from the ground, which is hard to achieve. Low levels of current flow through the body are painful. Higher levels cause the muscles to clamp and not release.

If  75 to 300 milliAmps (0.075 to 0.3 Amps) flowed through the heart, the heart will go into ventricular fibrillation, which is the same as a severe heart attack. The heart muscles twitch, or fibrillate, in self-perpetuating waves instead of the normal rhythm. The heart is unable to pump blood. Death follows in minutes.

Electricity deserves respect. Only a fool would take chances or shortcuts. A shock from a household 120 Volt circuit can, in some circumstances, be fatal. These cases usually occur when a person is wet and well-grounded and contacts some faulty equipment.

Less than two weeks before I wrote this, a 29 year old woman died from electrocution while swimming in a local lake. The newspaper story said that she touched a pipe near a dock and received a fatal shock. The pipe was connected to a pump that must have been malfunctioning. Most likely a $30 Ground Fault Interruptor (GFI) circuit breaker would have saved her life.

Electricity is powerful. Electricity can be deadly. But electricity is not frightening when it is understood.