Download presentation
Presentation is loading. Please wait.
Published byLynne Bryan Modified over 9 years ago
1
Electric Circuits Electric Current The amount of charge passing through a surface per second. Unit: ampere or amp (A) = coulombs/seconds The “conventional” current (I) is defined by the motion of positive charges → Benjamin Franklin 10/30/2015APHY1011
2
Electric Circuits Drift Speed The average speed of charges that make a current Usually ~ 0.1 mm/s The electric field is created throughout the wire so that all charges respond almost instantaneously The charges collide with atoms in the wire and proceed with a random walk The atoms get hotter due to these collisions → light ! 10/30/2015APHY1012
3
Electric Circuits Ohm’s Law and Resistance Unit: ohms (Ω) = volts/amps 10/30/2015APHY1013
4
Electric Circuits Resistivity What determines the value of R for a resistor? Type of material, length and thickness Temperature? Conductors, insulators, heating units, lights, etc. 10/30/2015APHY1014
5
Electric Circuits 10/30/2015APHY1015
6
Electric Circuits Energy and Electric Potential in a Circuit The PE of a charge is unchanged after traveling around a circuit PE is gained at the voltage source (ie. battery) and lost at the resistor (ie. light bulb) The sum of the ΔV around the circuit equals zero Voltage “drops” across a resistor 10/30/2015APHY1016
7
Electric Circuits Series circuits 10/30/2015APHY1017
8
Electric Circuits Series circuits 1. The current is the same everywhere in the circuit. I total = I 1 = I 2 = … 2. The total resistance of the circuit is R total = R 1 + R 2 + … 3. The sum of the voltages across each device equals the source voltage ΔV source = ΔV 1 + ΔV 2 + … 10/30/2015APHY1018
9
Electric Circuits Parallel circuits 10/30/2015APHY1019
10
Electric Circuits Parallel circuits 1. The total current in the circuit equals the sum of the current in each device. I total = I 1 + I 2 + … 2. The total resistance of the circuit is 3. The voltage across each device is the same. ΔV source = ΔV 1 = ΔV 2 = … 10/30/2015APHY10110
11
Electric Circuits Electric Power Energy transfer per unit time Unit: watts or joules/second Since it takes work (W) to move a charge (q) through a potential difference (ΔV) then we can say that 10/30/2015APHY10111
12
Electric Circuits Electric Power Overloading occurs when the circuit resistance drops to where the circuit carries too much current. Fuses or breakers are used to control the amount of current in a circuitFusesbreakers 10/30/2015APHY10112
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.