Electricity Technical Stuff

Electric Field An uneven distribution of charge produces an “ Electric Field” We can deduce this by an electric potential (∆V) with a voltmeter If there is a conducting pathway between the areas of uneven charge, the field will drive charge until the distribution is uniform

Electric Potential A battery maintains a difference by means of chemical reactions that physically transfer electrons (negative charges) Physics uses the Franklin Convention that states “+” charges flow through a circuit and return to zero at the negative terminal

Speed of Electricity The electric field propagates through a circuit at the speed of light, thus charge begins to flow everywhere in a circuit in an instant Don’t confuse with “Drift velocity” which is the movement of individual charges in a wire – Drift velocity is on the order of a millimeter/sec Current is the flow rate of how much charge moves past a given position in a time interval, – 1 amp is 1 Coulomb of charge in 1 sec

Electricity Math Stuff Ohms Law E=IR or V=IR either is acceptable and will be seen – E or V is a measurement of force in Volts – I is a measurement of current in Amperes or Amps – R is a measurement of resistance in ohms Ω Rearrangement of this equation happens often

Series Circuits Current is the same everywhere, thus the voltage drop across each resistance is proportional to the resistance The overall resistance is found by summing the individual resistance of the resistors. – ∑R = R 1 +R 2 +R 3 + … – First find the equivalent resistance then the current, then the voltage drop across each resistor.

Parallel Circuits The potential (Voltage) drop in each branch is the same The overall resistance decreases as the number of branches increases (more paths) The current IN EACH BANCH is inversely proportional to the resistance 1/R∑ = 1/R 1 + 1/R 2 + 1/R 3 + … First find the equivalent resistance, then the overall current, then the current through each branch