- 1 Basics of electricity
- 1.1 Charge (Q):
- 1.2 Current (I):
- 1.3 Voltage (V):
- 1.4 Resistance (r ):
- 1.5 Energy (E) and Work (U):
- 1.6 Power (P):
- 1.7 AC vs. DC Electricity
- 1.8 Series vs. Parallel Circuits
- 2 Powering a Computer Lab: Issues, Problems, and Some Solutions
- 3 Links
Basics of electricity¶
Charge (Q):¶
Charge is what causes electrical forces. Charge is to electromagnetism as mass is to gravity. The more charge something has the stronger force it emits. Unlike with mass objects can have positive or negative charge and objects with opposite charges (negative and positive) attract each other while objects with the same kind of charge (positive and positive, or negative and negative) repel each other. The charge of objects comes from the subatomic particles electrons and protons. Charge is measured in Coulombs (C ). One coulombs is equal to the charge of 6.24 × 1018 electrons.
Current (I):¶
In an electric circuit electrons flow through the wire of the circuit in a circle. Current is the rate at which the moves through a wire which is another way of saying current is the amount of charge that moves through a point in the wire every second. Current is measured in Amperes which are often called amps. One ampere equals one Coulomb per second.
Voltage (V):¶
Voltage is what makes current flow through a circuit. It is the change in potential energy per unit charge between two points on a wire. Water can be used as a good analogy: If a circuit was a river then the slope of the hill it is flowing down would be the voltage. Voltage is measured in Volts (V). 1 volt is the voltage across a wire when a one ampere of current dissipates one watt of power in that wire, a.k.a. 1 Volt = 1 Watt / 1 Ampere
Resistance (r ):¶
Resistance is what it sounds like. How much something resists the flow of current. Everything has electrical resistance including the wires you use. Resistance is measured in ohms (Ω). 1 ohm is the resistance between two points on a wire when 1 volt of potential difference applied to these points produces 1 ampere of current, a.k.a. 1 ohm = 1 volt / 1 amp.
Energy (E) and Work (U):¶
Energy is the amount of work that can be performed by a force. Work is the transfer of energy from one type to another. Devices that run on electricity turn electric energy into other kinds of energy. For example a light bulb turns electric energy into light energy (and heat energy as a byproduct.) Both work and energy are measured in joules (J). Energy is also often measured and sold in kilowatt hours (kW•h). 1 in kilowatt hour equals 3,600,000 Joules.
Power (P):¶
Power is the rate at which energy is transferred (or work is performed) or put more simply how fast devices change electrical energy into other types of energy. Power is measured in watts (W).
AC vs. DC Electricity¶
AC electricity stands for alternating current. In AC electricity the Current moves quickly back and forth at a steady interval. DC stands for direct current. With DC electricity the electricity only flows in one direction. The electrical systems (the power grid) in every country produce AC electricity. AC electricity is used instead of DC because it is easier to send over long distances. Also capacitors and inductors only work with AC electricity. Power plants produce AC electricity. Solar Panels produce DC electricity which is often changed to AC with an inverter. Batteries emit and store DC electricity. AC electricity can not be stored.
Series vs. Parallel Circuits¶
When components are connected in series they are all connected along a single path that electricity can flow through. When components are connected in parallel there are multiple paths that the electricity can flow through.
The straight lines represent wire.
The squiggly line with an R next to it represents a resistor.
The four lines with the + and - next to it represents a battery.
In the series circuit above all three resistors share the voltage of the battery, but in the parallel circuit each resistor gets the full amount of voltage from the battery. When batteries are in series their voltages add together. When batteries are in series their voltages do not add together, but the amount of current they can provide increases.
Powering a Computer Lab: Issues, Problems, and Some Solutions¶
Electricity In Other Countries¶
Different countries power outlets give out different amounts of voltage and move at different frequencies, so not all electronics work internationally. To see the differences between countries so you can make sure you get the right equipment and adaptors use the link below.
www.kropla.com/electric2.htm
Electricty in less developed areas is often unstable: Voltage may fluctuate and the power may flicker on and off or go out for long periods of time (but the power only needs to go out for a secound for you computer to turn off and for you to lose all your unsaved data.) Use a voltage stabilizer to avoid having equipment damaged by voltage changes and use a uninterruptable power supply (UPS) to avoid power fluctuations from turning off you equipment.
Energy Efficiency and Cost¶
Buying newer more energy efficient equipment over cheaper older equipment may save you money in the long run. You can save money on electricity use. If you are buying a solar power system energy efficient equipment can reduce the size (and thus the cost) of the solar panel you need to use. Since rechargeable batteries last longer when drained less, energy efficient equipment can also increase the life of your battery.
h4. Factors in energy consumption:-How often a monitor/cpu is on?
-Hours per day used, days per year,
-Actual energy usage (watts)
-Local energy costs, cost per Kw
Average wattage of a CRT monitor:
150 watts (awake)
30 (asleep)
LCD:
30-65 watts awake
3-4 watts asleep
Something to keep in mind: In cold situations, the extra energy created by CRT monitors can actually heat a room! But the same goes for hot summers, it may end up costing more in air conditioning.
h4. Generators:pollution and bad odor
Diesel
-lasts longer
-more fuel efficient
-lower RPM, and produce more torque at lower speeds (increases engine life and lowers noise)
-can break down quicker if not used frequently.
-a bit safer (see below)
Gasoline
-more combustible and can be ignited by static electricty.
-gasoline is a bit cheaper than diesel
-less expensive to repair
Solar Power¶
Solar power is a good option in areas with no or unreliable electricity. Solar power may also save you more money in the long run then paying for grid power or continuously buying fuel for a generator.
What you need for a solar power system:¶
- Solar panels – To produce electricity
- Rechargeable batteries – To store energy to use when it is cloudy or at night
- Charge controller – Stops the batteries from being over charged when or over drained reducing the batteries lifespan.
- Inverters – Turns DC to AC (or visa versa) so you can run equipment that requires that type of electricity
- Voltage stabilizer and uninterruptable power supply – If your solar system is also connected to the grid you need these to protect your equipment
Solar energy output¶
How much energy you are going to get from a solar panels depends on a couple of factors. The climate and area your power system effects how much energy you produce due to the angle of the sun relative the earth and climate conditions like clouds, fog, and rain. The angle of your solar panels is also important. Since the sun moves across the sky during the day choosing an angle that takes advantage of the during peak hours can improve your energy output. Buildings, trees and other obstacles can reduce the amount of energy you make if they shade your solar panels.
