Electricity

Electricity Multimeter •voltage •current •resistance Digital circuit probe measures digital logic levels Voltage tester •voltage level •rugged construction Clip-on ammeter measures current without direct connection Oscilloscope used to measure and examine voltage waveforms Sources of Electricity • • • • Heat Light Pressure Mechanical Magnetic action CURRENT - The rate of flow of electrons = One Coulomb Per Second Measurement Point = One Ampere AWG WIRE SIZES The larger the gauge number the smaller the actual diameter of the conductor. CONDUCTOR FORMS Solid wire Stranded wire Large stranded cable Lamp cord Multiconductor cable Resistors • • • • Series Parallel Units Symbol Ohm’s Law Most Important Law of Electricity • This law outlines the relationship between voltage, current and resistance in an electrical circuit. • Expressed as an equation: 1. I= Current in Amperes 2. V= is the potential difference measured in Volts 3. R= is the resistance measured in Ohms Ohm's Law For manyconductors of electricity, the electric current which will flow through them is directly proportional to the voltage applied to them. When a microscopic view of Ohm's law is taken, it is found to depend upon the fact that the drift velocity of charges through the material is proportional to the electric field in the conductor. The ratio of voltage to current is called the resistance, and if the ratio is constant over a wide range of voltages, the material is said to be an "ohmic" material. If the material can be characterized by such a resistance, then the current can be predicted from the relationship: Resistance The electrical resistance of a circuit component or device is defined as the ratio of the voltage applied to the electric current which flows through it: If the resistance is constant over a considerable range of voltage, then Ohm's law, I = V/R, can be used to predict the behavior of the material. Although the definition above involves DC current and voltage, the same definition holds for the AC application of resistors. OHM’S LAW FORMULAS Find Voltage Find Resistance V I= R V=IxR V R= Current equals voltage divided by resistance Voltage equals current multiplied by resistance Resistance equals voltage divided by current Find Current I Series Circuit • • • • Same current Voltage is additive Total Resistance = Add resistance Once open, the circuit fails. STEPS IN SOLVING PROBLEM Voltage R1 R2 R3 Total Current Resistance Power 12 V 3 mA 4 kΩ Ω 36 mW 6V 3 mA 2 kΩ Ω 18 mW 42 V 3 mA 14 kΩ Ω 126 mW 60 V 3 mA 20 kΩ Ω 180 mW STEPS IN SOLVING PROBLEM Voltage R1 R2 Total Current Resistance 24 V 0 Infinite (open) 0 0 4Ω 24 V 0 Infinite Power 0 0 0 Parallel Circuit • • • • Same Voltage Current is additive. Resistance is inverse. One opens, current is smaller than normal. STEPS IN SOLVING PROBLEM Voltage Current Resistance Power R1 24 V 3A 8Ω 72 W R2 24 V 1.5 A 16 Ω 36 W 24 V 1A 24 Ω 24 W 24 V 5.5 A 4.36 Ω 132 W R3 Total Electrostatic States ! ! " " " ! # ! $ $ " " " ! $ % ESD: A hare raising experience " !& ( ' ' ') Lightning strikes somewhere on Earth about 100 times each second! ' * " ! $ "" +* " ! % ! ! "