2 Current and Voltage Difference Electric Current-The net movement of electric charge in a single direction.Measured in Amperes (A)One Ampere is equal to 1 coulomb per secondIf there is no current, there is no NET movementMovement forward=movement backward=movement side-to-sideWhen an electric current is applied, there is still backward and forward movement, but the electrons drift in the direction of the current.Net movement
3 Before Current is Applied After Current is Applied
4 Current and Voltage Difference Related to the force that causes electric charges to flow.From area of high voltage to low voltageMeasured in volts (V)Electric CircuitsA closed path that electric current followsBattery, wire, lightbulbCurrent and electron flowFor historical reasons, we think of current as flow of positive chargesPositive charges do not flowDue to this, current is in the opposite direction of electron flowElectrons flow from lower to higher voltageCurrent is from higher to lower voltage
8 Dry-Cell Batteries Carbon Rod (positive) Zinc Container (negative) Moist paste (electrolyte)Allows electrons to flowBatteries in flashlightsMetals can be differentLithium, carbon, and lithiumsolutionCell phone battery
9 Wet-cell Battery2 connected plates made of different metals in an electrolyteUnlike the paste in dry-cells, the wet-cell has a liquidHas many cells connected together.Most common type is lead-acidLead and Lead dioxide in sulfuric acid solution
10 Electrical Outlets The 2 holes of an outlet have a voltage difference In the U.S. usually 120 V
11 Resistance Tendency of object to resist flow of electrons Takes some of the flowing electrons from the currentMeasured in ohms (Ω)This symbol is the capital form of the Greek letter “Omega”This is why batteries charging get warmThe resistor is taking some of the electrons, and converts the chemical energy to thermal energy
12 Ohm’s Law Current(A)=Voltage difference(V)/resistance(Ω) 𝐼= 𝑉 𝑅 Current is measured in Amps (A)𝐼= 𝑉 𝑅Where I is current
13 Example ProblemThe voltage difference in a graphing calculator is 6V, and the resistance is 1,200 Ω. What is the current through the batteries of the graphing calculator?Knowns: V=6V, R=1200 ΩUnknown: I=?Equation: 𝐼= 𝑉 𝑅Solve: 𝐼= 𝑉 𝑅 = 6𝑉 1200Ω=0.005 A
15 Guided PracticeAn object has a resistance of 60 Ω as a current of 2 A goes through it. What is the voltage difference across the object?
16 You Try It!The voltage in a device is 50 V, and the resistance is 5 Ω. What is the current in the device?
17 Types of Current Alternating Current (AC) Direct Current (DC) Type found in household electrical outletsChanges directionDirect Current (DC)Found in battery-powered devicesDoes not change directionConverters change types (ACDC)