A+ Computer Repair Lesson 4 Introduction to Electricity and Safety

Objectives: Define electricity, conductors, non-conductors, and semiconductors Define electricity, conductors, non-conductors, and semiconductors Describe how electricity flows Describe how electricity flows Distinguish between static and dynamic electricity Distinguish between static and dynamic electricity Distinguish among amps, volts, and watts Distinguish among amps, volts, and watts Describe features of fixed resistors, variable resistors, capacitors, and integrated circuit chips Describe features of fixed resistors, variable resistors, capacitors, and integrated circuit chips Identify basic electrical safety precautions Identify basic electrical safety precautions

What is Electricity?

Electricity is the flow of electrons through a circuit. Circuits are pathways made of conductive materials allowing electrons to pass through. Circuits direct the flow of electrons within electrical components, sending needed power to the right places. Electricity is the flow of electrons through a circuit. Circuits are pathways made of conductive materials allowing electrons to pass through. Circuits direct the flow of electrons within electrical components, sending needed power to the right places.

What is a conductor?

conductor is any type of material that allows electricity to freely flow through it. conductor is any type of material that allows electricity to freely flow through it.

What is a non-conductor?

The opposite of a conductor, a non-conductor, inhibits the flow of electricity. Some materials, such as wood or rubber, don't conduct electricity at all. The opposite of a conductor, a non-conductor, inhibits the flow of electricity. Some materials, such as wood or rubber, don't conduct electricity at all. Non-conductive materials or insulators are often used to shield, protect, or insulate wires and cable. Non-conductive materials or insulators are often used to shield, protect, or insulate wires and cable.

What is a semiconductor?

A semiconductor is a material that has been diluted with non-conductive materials to slow the progression of electron flow, but does not inhibit electricity completely. A semiconductor is a material that has been diluted with non-conductive materials to slow the progression of electron flow, but does not inhibit electricity completely.

Types of Electricity Dynamic Electricity Dynamic Electricity Static Electricity Static Electricity

Dynamic Electricity Constantly moving, never still, dynamic electricity is created with permanent magnets, coils, wires, and magnetic fields that promote the flow of electrons. Constantly moving, never still, dynamic electricity is created with permanent magnets, coils, wires, and magnetic fields that promote the flow of electrons. Electric generators, alternators, and transformers all work to produce dynamic electricity which can be very powerful and can travel great distances. Electric generators, alternators, and transformers all work to produce dynamic electricity which can be very powerful and can travel great distances.

Static Electricity Static—or stationary—electricity occurs as a result of friction. Static—or stationary—electricity occurs as a result of friction. electrons from one object build up on the surface of the second object, giving the second object a negative charge. electrons from one object build up on the surface of the second object, giving the second object a negative charge.

What is current?

Current, measured in amperes (amps for short), describes the amount of electricity traveling from a point of greater electricity to a point with less electricity, always taking the path of least resistance. Current, measured in amperes (amps for short), describes the amount of electricity traveling from a point of greater electricity to a point with less electricity, always taking the path of least resistance.

Two different designations for current: Alternating Current (AC) Alternating Current (AC) Direct Current (DC) Direct Current (DC)

What type of current does a computer use? What type of current does a computer use?

How is electricity measured? Amps - or ampere, is a measure of the rate of flow of electrical charge. Amps - or ampere, is a measure of the rate of flow of electrical charge. Ohms - An ohm is a measurement of the resistance to the flow of electricity. Ohms - An ohm is a measurement of the resistance to the flow of electricity. Farad - Capacitance, measured in units of farads (F) is expressed as the ratio of stored charge Farad - Capacitance, measured in units of farads (F) is expressed as the ratio of stored charge Volts - "Electrical pressure" is measured in volts. Volts are measured by finding the difference in electrical pressure between two points. Volts - "Electrical pressure" is measured in volts. Volts are measured by finding the difference in electrical pressure between two points. Watts - A measure of electrical power. Watts are calculated by multiplying volts by amps in a system. Watts - A measure of electrical power. Watts are calculated by multiplying volts by amps in a system.

Basic Electronic Components Variable Resistor - A stereo's volume control is one example of a variable resistor. Variable Resistor - A stereo's volume control is one example of a variable resistor.

Basic Electronic Components Fixed Resistor - Fixed resistors, color-coded to identify their resistance values, do not adjust. Fixed Resistor - Fixed resistors, color-coded to identify their resistance values, do not adjust.

Basic Electronic Components Capacitor - stores electrical charges and is used in power supplies and timing circuits. Capacitor - stores electrical charges and is used in power supplies and timing circuits.

Basic Electronic Components Integrated Circuit Chip - is a device consisting of a number of connected circuit elements, such as transistors and resistors. The IC is constructed on a single chip of silicon crystal or other semiconductor material. Integrated Circuit Chip - is a device consisting of a number of connected circuit elements, such as transistors and resistors. The IC is constructed on a single chip of silicon crystal or other semiconductor material.

Continuity Continuity is a term that describes the condition of an electric circuit. When a circuit breaks, it loses its continuity and will no longer be able to power a device. Continuity is a term that describes the condition of an electric circuit. When a circuit breaks, it loses its continuity and will no longer be able to power a device.

Short Circuit A short circuit basically occurs when electricity- carrying circuits that should not come in contact, come in contact and cause large amounts of electricity to be dumped onto a circuit. A short circuit basically occurs when electricity- carrying circuits that should not come in contact, come in contact and cause large amounts of electricity to be dumped onto a circuit.

Ground Wire A ground is some material that has the capability to absorb a lot of electricity without being affected, which is why the earth is used as the ground for the public electrical grid. A ground is some material that has the capability to absorb a lot of electricity without being affected, which is why the earth is used as the ground for the public electrical grid.

Preventing Electrical Shocks Avoid using faulty circuits, old or corroded electrical grounds components, and exposed wire. Avoid using faulty circuits, old or corroded electrical grounds components, and exposed wire. Unplug any sensitive computing equipment during an electrical storm. Also, purchase spike and surge protectors, line conditioners, and uninterruptible power supplies to further safeguard equipment and data. Unplug any sensitive computing equipment during an electrical storm. Also, purchase spike and surge protectors, line conditioners, and uninterruptible power supplies to further safeguard equipment and data.

Preventing Electrical Shocks Never open a computer's chassis, install internal hardware, or tinker with a computer's power supply unit while a computer is plugged in or when you are not properly grounded. Never open a computer's chassis, install internal hardware, or tinker with a computer's power supply unit while a computer is plugged in or when you are not properly grounded. Never stand on a damp or wet floor where electrical wires are exposed. Never stand on a damp or wet floor where sources of electricity could touch the floor. Never stand on a damp or wet floor where electrical wires are exposed. Never stand on a damp or wet floor where sources of electricity could touch the floor.

Preventing Electrical Shocks  Make sure that extension cords and power strips are in excellent condition. Discard any cords or power strips if their condition is at all questionable.  Always be aware of and careful with electricity: treat electricity with respect.