Presentation on theme: "Applied Physics and Chemistry Circuits Lecture 1"— Presentation transcript:
1Applied Physics and Chemistry Circuits Lecture 1 Current ElectricityApplied Physics and Chemistry Circuits Lecture 1
2Electric Current Current is flow of charges There must be a complete loop (closed) for flow to occurFlow from high potential to low potentialAs potential decreases, work is done by chargesConventional current is flow of positive chargesDo positive charges actually flow?
3Electric Current Current may be direct or alternating Direct current: flows in one directionAlternating current: flows back and forth
4Electric Circuit Required for current electricity Closed loop or conducting path from high to low potentialMust have four parts:Source of charges (area of high potential)Path for chargesDevice that reduces potential energySink (area of low potential)
5Electric Circuit Energy is conserved in the circuit Charge is conserved in the circuitEnergy carried by current depends on charge and potential differenceΔE = qVRemember, V is the potential difference1 V = 1 J/C
6Electric Current Current is rate of flow of electric charge Measured in Coulombs / sec1 C/s = 1 A (Ampere)Symbol for current is I
7Electric PowerRate of energy transferMeasured in Watts1W = 1 J/s
8Electric Power Since P = E/t And E = qV And q= It Then P = VI Power is current times the potential difference.
10Electric PowerIf the current through a motor is 3 A and the potential difference is 120 V, what is the power of the motor?Known: I=3A V=120 VEquation: P=IVP=(3A)(120V)=360 W
11Electric Power Problem 2 A 6 V battery delivers 0.5 A of current to an electric motor. What is the power rating of this motor? What we know: V = 6V I = 0.5 A Equation: P = IV Substitute: P = (0.5 A)(6 V) Solve! P = 3 W
12Electric Power Problem 2 Contd. How much energy does the motor use in 5.0 minutes?What we know:P = 3 W t = 5.0 min = 300 sEquation:P = W/t which means P = E/t and E = PtSubstitute:E = (3 W)(300 s)Solve!E = 300 J