Chapter 25 EM Induction and EM Waves (Powerpoint of tonight’s lecture: here) F = 9VB SinΘ Example The sliding conductor rod on the diagram below is 15.0 cm long and moves with a speed of 20m/s to the left. Total resistance of the circuit is 5Ω and the magnetic field is 0.5T. […]

## Physics 115: Lecture 19

On the Exam Electric Potential Energy (U) Electric Potential ( Equiptential Lines lines lines lines are more closely spaced DC Circits Battery (source of Capacitors (store charge) ( dielectric constant Resistors (R) (Ohm’s Law) Recall original Ohm’s Law Muiltiple Capacitors Parrellel Series Muiltiple Resistors Parrellel Series Kirchoff’s Rules 1st Rule for a closed path […]

## Physics 115: Lecture 18

Concept Properties of the magnetic force: Created by currents (moving charges) (source current) Only affects (applies a force on) moving charges (currents) (velocity (test current) Case 1 Force on a moving charge, due to aa current. A current creates a uniform magnetic field . A positive charge Q, moving at velocity in this field, will experience […]

## Physics 115: Lecture 17

Example Work done to charge a capacitor: V =3V C = 0.5F Example Example In parallel, It can be shown, for N resistors in parallel, Example A 2μF and a 4μF capacitor are connected in series across an 18V battery A) Calculate the final charge on each B) Calculate […]

## Physics 115: Lecture 16

Example What is the current flows? It does not flow if both batteries are of the same voltage. If they are different then there would be a flow. Discribe the circuit as shown. V1 – IR1 – IR1 – IR2 – V2 – IR2 – IR3 = 0 Solve Concept Kirchoff’s 1st Loop Rule The […]

## Physics 115: Lecture 15

Ohm’s Law Electromotive force It is called “emf” emt is equivlent to voltage (but not really) It is not a force. Concept Concept Resistors in series, Resistors in parallel, Example The voltage drop across both bulbs (A to B) is, We suppose there is an “equivalent resistance” such, Equating, […]

## Physics 115: Lecture 14

Ohms Law Example A 3V potential difference is wired to a bulb of resistance 4.4 . What current passes through the bulb? Concept Brightness of a bulb? Related to the power Energy transformation over time S.I. Unit: “watt” [W] Named after James Watt Power from a light bulb Concept If […]

## Physics 115: Lecture 13

Concept Example Electric Current (i or I) Movement of charge along a path. Amount of charge that passes a given point in a “circuit” per second unit of I is C/s The unit is A = C/s = “ampere” Magnify the Wire Define current density (J) J = I/Area units = Amps/m^2 Properties of […]

## Physics 115: Lecture 12

Example Plates are circular, r = d = Work Example Example Effect of Dielectric on Capacitor Recall, for vacuum between the plates, If not vacuum, then New Constant! It is the “dielectric constant” It is unitless The equation is: Some values of Vacuum = 1 Dry air = 1.00054 Moist air (at […]

## Physics 115: Lecture 11

Conductors Charge moves very easily (very low resistance.) Metals Water with ions Insulators Charge moves, but very very, very slowly (high resistance) Glass Example A) Properties of Conductors inside a conductor B) The net volume charge density inside is zero C) Any net (excess) charge resides on the surface D) V is constant everywhere in […]