How Things really Work The Physics behind Everyday Life Thur July 7: Morning Session 3: 9 – 11:30 PM. Electrodynamics and Magnetism Learning Objectives: Understand the basic structure of an atom and which parts are involved in magnetism, static and dynamic electricity Understand how magnetism creates electricity. Identify what causes a negative and positive charge Understand the difference between a static charge and an electrical current Understand the concepts of voltage, amperage and resistance

Lab 1: (from Lab 102 Exp 6) - Resistance & Ohms Law Theory: A basic resistance circuit is the simplest circuit and is used in an ordinary flashlight. There is a battery, which acts as a constant voltage source, and a light bulb, which is in effect a special resistor. In the figure below a schematic diagram of this circuit is shown, with the various parts labeled. I = V/R or V = IR or R=V/I

Series Combinations of Resistance

Parallel Combinations of Resistance 1/Req = 1/Rl + 1/R2 + 1/R3

Resistivity of a Wire Resistivity is just the inverse of conductivity. We use the symbol σ for the conductivity, and ρ for resistivity. Thus σ = 1/ρ and R = resistance of a wire = ρL/A L = Total length of the wire, A = cross- sectional area of the wire

Lab 2: (from Lab 102 Exp 5) – Capacitors & Dielectrics Theory: A capacitor or condenser is a passive electronic component consisting of a pair of conductors separated by a dielectric. When a voltage potential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the plates. One of the main uses of capacitors is to store static charge. The relationships among: Capacitance (C), Charge (Q), Voltage difference (V) Plate Area (A), Plate Separation (d), Dielectric Constant (εo) = 8.85 x10-12C2/Nm2. in a parallel plate capacitor can be summarized by two equations C = Q/V and C = εoA/d

Capacitors in Series Ceq = 1/Cl + C2 + C3

Resistors in Parallel Ceq = Cl + C2 + C3

Lab 3: (from Lab 102 Exp 7) – The Wheatstone Bridge Theory: The Wheatstone Bridge circuit is used to determine the unknown resistance Rx of a resistor. This is done by adjusting the relative values of the R1 and R2 until the galvanometer reads zero, and the balance condition is met. In our apparatus, R1 and R2 are made of a single piece of high resistance wire 1 m long. Figure A shows the basic Wheatstone Bridge and figure B is how the circuit is arranged on the apparatus you will be using.

Wheatstone Bridge

Color Codes for Resistors ColorDigitMultipli er ColorDigitMultipli er ColorDigitMultipli er Black01Yellow410 4 Gray810 8 Brown110Green510 5 White910 9 Red210 2 Blue610 5 Orange310 3 Violet710 7

Lab 4: (from Lab 102 Exp 8) – DC Circuit Analysis Theory: In this experiment we'll explore in more detail how Ohm's law determines the volt­age drops across and currents through resistors in various resistance circuits. This experiment also gives us a convenient opportunity to explain a little bit about the importance of fuses and light bulbs in general. Circuit Analysis –We'll apply a few simple rules to study some simple circuits. Our basic goal will be to understand how the current flow is divided up between the multiple possible paths between the –+ and - terminals in the battery. Series Circuits Parallel Circuits

Figure 11

Figure 12

Lab 5: (from Lab 102 Exp 9) – Magnetism

A B C Fig. 13 A, B, and C

AB Fig. 14 A and B