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Transcript
Ohm’s Law Conceptual Relationship Ohm’s Law Is usually written down as an equation of the form: V = IR Conceptually, it often makes more sense to write the equation as: I = V/R But what does this actually MEAN in terms of our circuit??? Current I is the variable for current. Current is the flow of electrons through the wire. You can think of this like cars on a freeway. The more cars that are going by in a minute, the more current there is. Generally, the more energy each electron (or car) has, the more current there is. Voltage • Voltage is the amount of energy given to each electric charge. • The voltage comes from the battery and the battery alone so the other circuit elements do not affect or CHANGE the voltage. Resistance • Resistance is the opposition to the current. This is anything that makes it harder for current to flow. • Going back to our freeway example, resistance is all the things that cause traffic (too many cars at once, not enough lanes, accidents, the road is in terrible shape, etc.) • In the circuit itself, resistance comes from the resistors, which in our class is usually the light bulbs. So other circuit elements don’t affect the resistance. Back to Ohm’s Law • Remember, Ohm’s Law is an equation that expresses the relationship between these three variables. • Conceptually Ohm’s Law makes more sense if we write it like this: I=V/R Because voltage is only affected by the battery and resistance is only affected by the light bulbs. • CURRENT is being affected by both of voltage AND resistance – not the other way around. Back to Ohm’s Law I=V/R So if the voltage goes up, say by adding more batteries, the current will go up too!! Resistance won’t be affected by this change. If the resistance goes up, say by adding more resistors the current will go down. The voltage would not be affected by this change.