Theory: Current Current is charge in motion Most of the time we think about electrons moving through metallic wires The flow rate of charge is measured in couloumbs/second or Amperes (Amps) • charge/time = couloumbs/sec = Amperes 1 Amp = 1.6 * 1019 electrons / sec

Theory: Current Current is charge in motion Most of the time we think about electrons moving through metallic wires The flow rate of charge is measured in couloumbs/second or Amperes (Amps) • charge/time = couloumbs/sec = Amperes 1 Amp = 1/1.6 * 1019 electrons / sec

Power “An interesting fact to note is that it takes less alternating current (AC) to do the same damage as direct current (DC). AC will cause muscles to contract, and if the current were high enough, one would not be able to let go of whatever is causing the current coursing through the body. The cut-off value for this is known as the "let-go current". For women, it is typically 5 to 7 milliamperes, and for men, typically 7 to 9 milliamperes. This is dependent on the muscle mass of the individual. In general, current that is fatal to humans ranges from 0.06 A to 0.07 A, depending on the person and the type of current.” http://hypertextbook.com/facts/2000/Jack Hsu.shtml American Wire Gauge Recommended Maximum Fuse Size 00 awg 400 amps 0 awg 325 amps 1 awg 250 amps 2 awg 200 amps 4 awg 125 amps 6 awg 80 amps 8 awg 50 amps 10 awg 30 amps 12 awg 20 amps 14 awg 15 amps 16 awg 7.5 amps

Power Consideration Component Volts Amps Power Consumption Magnetron 4.1 kV 0.171 amps 1000 W Fan 120 V 0.7 amps 39 W Light 240 V 0.0833 amps 20 W Turntable 120 V 0.025 amps 3W Buzzer 10 V 0.010 amps 0.1 W Controller 3.3 V 0.45 Amps 1.485 W Camera 5V 0.075 Amps 0.375 W Touch Screen 5V 0.155 Amps 0.76 W 1.67 Amps 1064.72 W Total: All small appliances must be designed to operate within 15amp circuit. Total power consumption must be less than 1800 watts.

Electric Current • Electric current is the flow of positive charge. 1 Amp = 1 Coulomb per second. • Electric current is an effect of the flow of free electrons which carries negative charge. (6.28 x 1018 electrons = -1 Coulomb). • Positive charge flow (current) and negative charge flow (electron flow) are the same in magnitude but in the opposite direction. • By convention, current flow is used in analyzing circuits. Electron flow is used ONLY for describing the physical behavior of electric conduction of materials. Ping Hsu Introduction to Engineering – E10 Bubble Flow (current flow) Water flow (electron flow) 14

Electric Current • Electric current is the flow of positive charge. 1 Amp = 1 Coulomb per second. • Electric current is an effect of the flow of free electrons which carries negative charge. (6.28 x 1018 electrons = -1 Coulomb). • Positive charge flow (current) and negative charge flow (electron flow) are the same in magnitude but in the opposite direction. • By convention, current flow is used in analyzing circuits. Electron flow is used ONLY for describing the physical behavior of electric conduction of materials. Ping Hsu Introduction to Engineering – E10 Bubble Flow (current flow) Water flow (electron flow) 20

Introduction • Operational Amplifier (Op-Amp) name comes from the fact that it was originally used to perform mathematical operations. • Op-Amp is an active circuit element which is basic component used to build analog circuits. • Op-Amp is a low cost integrating circuit consisting of transistors, resistors, diodes and capacitors. • Op-Amps are two-port networks in which the output voltage or current is directly proportional to either input voltage or current. Four different kind of amplifiers exits: • • • • Voltage amplifier: Av = Vo / Vi Current amplifier: Ai = Io / Ii Transconductance amplifier: Gm = Io / Vi Transresistance amplifier: Rm = Vo / Ii • In negative feedback mode, the op-amp always “wants” both inputs (inverting and non-inverting) to be the same value. If the op-amp inputs are not the same value, the op amp output will go positive or negative saturation, depending on which input is higher than the other. • Op-Amps are commonly used for both linear and nonlinear applications: Inverting/Non-inverting Amplifiers, Variable Gains Amplifiers, Summers, Integrators/Differentiators, Filters (High, Low, Band Pass and Notch Filters), Schmitt trigger, Comparators, A/D converters.

Example 2.3—Calculating flux loss for no-load conditions The exciting circuit, Io , is a no-load current. Let’s calculate the exciting circuit in the primary of a transformer using data from Example 2.3: Given a 25-kVA, 2400—240 V, 60 Hz, draws 138 W at no-load condition with a .210 lagging power factor (current into a coil lags the voltage). 1st get the phase angle Ѳ…cos-1(.210) = 77.88° 2nd insert the power factor angle of 77.88° into the formula for the phase difference between the voltage and current: Ѳ = Ѳv – Ѳ i Using 0° phase for Ѳv gives: 77.88° = – Ѳi therefore Ѳi = – 77.88° This value is the angle the current vector I 0 makes with the vector Ife We’ll need this information to calculate the I M current but first let’s do the core-loss component that draws real power: P core loss = Vt ∙ Ife Insert known values: 138 = 2400 ∙ Ife Solve for the unknown: Ife = .0575 amps …giving us the amplitude for the vector Ife Utilize this value and a trig formula from the power triangle: cos Ѳi = Ife / Io Insert known values: .210 = .0575/ Io yields up Io = .2738 amps Using Io = Ife + IM we can solve for IM = Io - Ife → .2738 - .0575 = .268 amps Summary: Io = .2738 amps, Ife = .0575 amps, IM = .268 amps