U3e-L3 1.Why are the + and – symbols unnecessary when drawing the power source in an electric schematic? 2.A ______ circuit occurs when the positive terminal is connected directly to the negative terminal by a conductor, with no resistance. February 25, 2010 DRILL Short 1. The length of the lines tell you which is positive and which is negative

U3e-L3 1.What is a schematic? 2.Which of the following is a schematic? Electric Schematics A schematic is a diagram that represents the elements of a system without using realistic pictures

Complete problem #5 on your worksheet Problems – Joule’s Law U3e-L3

5.A Honda Insight (hybrid) has a 144 Volt battery system in its trunk. The electric motor that the batteries power can generate 20,000 Watts of power. Sketch a schematic diagram of this circuit. What is the current traveling through this high voltage circuit? 1)Write the given information: V = 144 volts P = 20,000 watts I = ? Problems – Joule’s Law A schematic is a diagram that represents the elements of a system without using realistic pictures U3e-L3

1)Write the given information: V = 144 Volts P = 20,000 Watts I = ? 2)Sketch a schematic diagram of the circuit: Start with power source Add conductors Add load Add current Problem #5 – Joule’s Law V = 144V I = ? - + P = 20,000 W U3e-L3

1)Write the given information: V = 144 Volts P = 20,000 Watts I = ? 3)Rearrange, Substitute, and Solve Problem #5 – Joule’s Law 5V.7A R = ? 2)Sketch a schematic diagram of the circuit: P = V x I I = 20,000W / 144V I = A I = P / V U3e-L3

Homework Problems #2 and 3 Review Problems – Joule’s Law U3e-L3

1)Write the given information: V = 9 Volts I =.02 Amps R = ? 3)Rearrange, Substitute, and Solve Homework Problem #2 9V.02A R = ? 2)Sketch a schematic diagram of the circuit: V = I x R R = 9V /.02A R = 450 Ω R = V / I U3e-L3

This is how alternating current (AC) power sources are represented schematically 1)Write the given information: V = 120 Volts I = 5 Amps R = ? 3)Rearrange, Substitute, and Solve Homework Problem #3 120V 5A R = ? 2)Sketch a schematic diagram of the circuit: V = I x R R = 120V / 5A R = 24 Ω R = V / I U3e-L3

U3e-L1 The unidirectional flow of electrons. Direct current is current travelling in 1 direction – from the negative terminal to the positive terminal. Direct current is used in almost all electronic systems as the power supply. Batteries are a sign of direct current. Direct Current one I

1.5 V Measuring the voltage of a direct current power supply: The voltage is constant. Direct Current U3e-L3

If voltage is constantly 1.5 V, what does its graph over time look like? Direct Current Time (seconds) Voltage (volts) V U3e-L3

Electrons flow back and forth through an electric circuit. Most artifacts you plug in. Alternating Current 120V R = ? 120 V +- U3e-L3

If voltage is alternating 120 V to -120 V, what does its graph over time look like? U3e-L3 Alternating Current Time (seconds) Voltage (volts) /-120 V

Resistors in series are added: U3e-L3 Resistance Calculations R1R2R3 R = R1 + R2 + R3 T Total Resistance:

Resistors in parallel: add their reciprocals U3e-L3 Resistance Calculations R1R2R3 R R1 + R2 + R3 T Total Resistance: =

Calculate the resistance in the following circuit: U3e-L3 Resistance Calculations R = R1 + R2 + R3 T Total Resistance: 100 Ω R = 100 Ω Ω Ω T R = 300 Ω T

Calculate the resistance in the following circuit: U3e-L3 Resistance Calculations 100 Ω R R1 + R2 + R3 T Total Resistance: = 100 Ω

= U3e-L3 Resistance Calculations R R1 + R2 + R3 T = R T 1 = R T 1.03 = (Multiply both sides by Rt) 1 =.03 x Rt Rt = 33.3 Ω

U3e-L3 1.Complete the worksheet on electrical problems using Joule’s and Ohm’s Laws. 2.Solve for V, I, R, and P for each of the six problems.