1. Parallel Circuits Paul Barnes

2. Contents Slide 3………What you want to find Slide 4………Finding Voltage for simple currents. Slide 5………Finding Resistance Slide 6………Finding Current Slide 7………Complicated Parallel Circuits Slide 8………Video/ActivPhysics Example

3. What you want to find Voltage (Volts) Resistance (Ω) Current (Amperes) *Arrows in diagram represent the flow of electrons. (Opposite of the direction of the E field.)

4. Finding Voltage for a simple parallel circuit Voltage across each portion of the parallel circuit is equal to the total voltage across the parallel circuit.

5. Finding Resistance Use the equation; 1/(R total ) = 1/R 1 + 1/R 2 + …… + 1/R n, where R total refers to the Resistance across the entire parallel part of the circuit and the individual R n ’s refer to the individual resistors in parallel.

6. Finding Current To find current, use Ohm’s Law for any individual resistance across a parallel circuit or for the total resistance across the parallel circuit. Ohm’s Law: V = I*R. (V = volts, I = current, R =resistance) This equation can be rearranged to solve for current: I = V/R.

7. Complicated Parallel Circuits Voltage: If there are parallel circuits within parallel circuits such as in the diagram below, you must keep in mind that voltage is the same across each piece of a parallel circuit. Since there are no resistors in series below, all of the individual resistors experience a voltage difference equal to the voltage difference of the battery (in this case, 10V). Resistance: resistance is calculated the same way, but the smaller parallel componentm (labeled A), must be calculated first to calculate the larger parallel component (labeled B). Current: Current through each compoment can still be calculated using Ohm’s law in the same way.

8. Video/ActivPhysics Example http://www.youtube.com/watch?v=UgH iyPTDCLA http://www.youtube.com/watch?v=UgH iyPTDCLA ActivPhysics link: http://media.pearsoncmg.com/bc/aw_y oung_physics_11/pt2a/Media/DCCircui ts/1202DCParallel/Main.html http://media.pearsoncmg.com/bc/aw_y oung_physics_11/pt2a/Media/DCCircui ts/1202DCParallel/Main.html (I didn’t find ActivPhysics very helpful for this, but feel free to give it a shot)