A current of 2.0 A is flowing in a circuit. How much charge passes a given point in the circuit in 30 seconds? I = Δq t 2.0 A = Δq 30 s (2.0 A)(30 s) = Δq 60 C = Δq
5 electrons pass a given point in 1 x 10 -18 s. What is the current?
Resistance A measure of how easy or difficult it is for current to flow
Ohm’s Law Units = ohm (represented as Ω) Georg Simon Ohm 1787-1854
A potential of 120 V draws 15 A of current. What is the resistance? A transistor radio of 0.2 A of current is operated by a 9 V battery. What is the resistance?
When solving for other expressions, here’s the electrician’s trick: V IR R = V =IR I =
75 V flows through a 15 Ω resistor. What is the current? A 60 Ω resistor allows 0.4 A of current to flow. What is the voltage?
What is the potential difference across a 2.0 Ω resistor that draws 2 C of charge per second?
Graph of V vs. I Current (amps) Voltage (volts) Slope is RESISTANCE
Resistance Increases when: Length of conductor increases/decreases Cross sectional area of conductor increases/decreases Temperature of metal conductor increases Temperature of non-metal conductor decreases Area length
Resistance of Conducting Wire R = Resistance (Ω) ρ = Resistivity (Ωm) L = Length (m) A = Cross Sectional Area (m 2 )