current, voltage, and resistance in a circuit. characteristics of a circuit – v is voltage (volts...
TRANSCRIPT
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
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
Resistance
• Resistance depends on three properties– Material (resistivity )– Cross-sectional area– length
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)
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)
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”?
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