Current, Voltage, and Resistance in a circuit

Characteristics of a circuit V is voltage (volts – V) I is current (amperes or amps – A) R is resistance ( ohms - Ω)

Voltage Also called Potential (don’t confuse this with potential energy) Voltage is the Energy per Coulomb provided to the circuit. Potential differences are what drive current in a circuit

Voltage Measured in volts

How batteries create a voltage difference

Current Current is the rate at which charges flow through a circuit 1 coulomb in 1 sec = 1 Ampere (Amp)

Direction of the Current flow CONVENTIONAL CURRENT Direction positive charges would move Away from higher potential (+ on the battery) ELECTRON CURRENT Direction electrons would move Away from lower potential (- on the battery)

Resistance The electrons encounter obstacles as they move through a circuit (this is what creates resistance to the current) Measured in ohms Ω

Resistance Resistance depends on three properties Material (resistivity 𝜌 ) Cross-sectional area length

In Summary

Voltage in a circuit When voltage sources are connected in series and in the same direction, their voltages add together. If they’re in opposite directions you subtract their voltages (it’s like they’re working against each other)

Resistance in a circuit In a series circuit, you add each of the individual resistances

In a parallel circuit, it’s a little more complex.

Chanting Ohmmmmm on the AP exam has not been proven to be effective. Current in a circuit The amount of current flowing through a given part of a circuit is determined from the resistance and the voltage using ohm’s law Chanting Ohmmmmm on the AP exam has not been proven to be effective.

Ohm’s Law V = IR V is voltage (volts – V) I is current (amperes or amps – A) R is resistance ( ohms - Ω)

Determining Voltage, Resistance, and Current in a circuit

That’s great if you have a purely series or parallel circuit but what if there’s a combination of the two, some kind of, I don’t know, “combination circuit”?

SOLVING THE COMBINATION CIRCUIT

The basic strategy is to simplify the circuit into a series circuit.

Power The power dissipated in a circuit element equals: P=IV The total power dissipated by the elements in a circuit must equal the power supplied by the battery Basically you have to use all the power and you can’t use more power than you’re given