1 / 4

Physics 18: Electric Currents

Physics 18: Electric Currents. Christopher Chui. The Electric Battery. Volta originated the battery, which transforms chemical energy into electrical energy All batteries have electrodes and electrolytes

gunnar
Télécharger la présentation

Physics 18: Electric Currents

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physics 18: Electric Currents Christopher Chui Physics 18: Electric Currents - Christopher Chui

  2. The Electric Battery • Volta originated the battery, which transforms chemical energy into electrical energy • All batteries have electrodes and electrolytes • An electric cell is a device that has electrodes and electrolytes. Several cells connected together is a battery • In a single cell, electrons are drawn from the positive terminal. When the electrodes are connected with a conductor, then the electrons complete the circuit. Thus, the current flows. By convention, current flows from positive terminal to negative terminal Physics 18: Electric Currents - Christopher Chui

  3. Electric Current and Ohm’s Law • A flow of charge from one terminal to another is called an electric current, I = DQ/Dt • The unit for current is Ampere (1775-1836), 1 A=1 C/s • Conventional current starts from +ve terminal to the –ve terminal; electron flow is opposite • Ohm’s law: V = IR, R is in ohms • Resistor color code: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9 • Tolerance: gold 5%, silver 10%, no color 20% • Resistance R of a metal wire is proportional to L and inversely proportional to cross-sectional area A • R= r L/A; r is resistivity, which depends on the material • Effect of temperature: rT = ro [1 + a(T-To)] Physics 18: Electric Currents - Christopher Chui

  4. Electric Power • P = power = energy transformed/time = QV/t = IV • P = I(IR) = I2R = V2/R • A short circuit means that 2 wires have crossed so that the path of the current is shortened • Fuses and circuit breakers are safety devices to prevent shorts in the household • When current flows steadily in one direction, it is DC • AC currents alternate from +ve to –ve continuously • In AC, V = Vo sin 2pft; Vo=peak voltage, I=Io sin 2pft • Average power = ½ Io2R = ½ Vo2/R = Irms2R • Irms = Io/sqrt(2) = 0.707Io and Vrms = Vo/sqrt2=0.707Vo • I = DQ/Dt = neAvd Physics 18: Electric Currents - Christopher Chui

More Related