Presentation on theme: "Mrs. Cockrell PAP Physics"— Presentation transcript:
1Mrs. Cockrell PAP Physics Electric CircuitsMrs. CockrellPAP Physics
2Electric Current Flow of electrical charge The rate at which electric charges move through a given area.FormulaI = q/tI = current (A)q = charge (C)t = time (s)
3DC vs AC Direct Current (DC) Alternating Current (AC) All charges move in one direction from an area of high potential to an area of low potentialAlternating Current (AC)Charges move back and forth generating a flow of charge
4Conventional Current vs Flow of Electrons Conventional Current – Flow of positive chargesFlow of electrons – Movement of electronsThey are opposite directions of each other
5Sources of CurrentBattery – Uses chemical energy to generate DC currentPhotovoltaic Cell (Solar Cell) – Converts sunlight into DC currentAn inverter changes it to ACGenerators – Converts kinetic energy into AC.
6Potential Difference Caused by a separation of opposite charges Often times called Voltage or electric potential
7Resistance The opposition to electron flow through a conductor Resistance is affected by length, area, type of material, and temperature
8Ohm’s Law Formula Example V = IR V = Potential Difference (V)I = Current (Amperes or Amps)R = Resistance (Ohm’s or Ω)ExampleA 1.5 V battery is connected to a small light bulb with a resistance of 3.5Ω. What is the current in the bulb?
9Kilowatt-Hour How electric companies charge for service. You pay for energy used, not power.1KW-Hr = 3.6 x 106 JExample:A television set draws 2.0 A when operated on 120 V. (A) How much power does the set use? (B) If the set is operated for an average of 7.0 h/day, what energy in kWh does it consume per month? (30 days) (C) At 11 cents per kWh, what is the cost to operate the set per month?
10Electric CircuitsSet of electrical components connected so that they provide one or more complete paths for the movement of chargesClosed circuit – complete path, one in which electrons are free to moveOpen circuit – not a complete pathLight Bulbs contain a complete conducting path
11Diagramming a circuit Wire or Conductor Resistor Bulb or Lamp Schematic DiagramGraphical representation of an electrical circuitWire or ConductorResistorBulb or LampPlugBatterySwitchCapacitor
12ExamplesDraw a schematic diagram of two resistors connect in a line with a battery.
13Series CircuitA circuit or portion of a circuit that provides a single conducting path without junctionsCurrent through each resistor is the same but varying potential differenceTotal Resistance (Equivalent Resistance) – sum of all resistancesSum of the voltages = total voltageAll elements must be present to get electron flow
14ExampleA 9.0V battery is connected to four light bulbs in series of resistances 2Ω, 4Ω, 5 Ω, and 7 Ω. Draw the schematic diagram and calculate the equivalent resistance and current in the circuit.
15Parallel CircuitsTwo or more components in a circuit that are connected across common points or junctions, providing separate paths for the current.Resistors have the same potential difference but varying currentsSum of the currents = total currentEquivalent Resistance is calculated by using the reciprocal relationshipNot all elements must be present in order to operate
16ExampleA 9V battery is connected to four resistors in parallel with the following resistances. 7 Ω, 5 Ω, 4 Ω, and 2 Ω. Draw the schematic diagram and find the equivalent resistance for the circuit and the total current in the circuit.
17Complex CircuitsWhen wiring a home or building complex circuits are used.Circuit breakers and fuses are placed in the circuits that open when the current becomes too high.To calculate equivalent resistance, simplify the circuit into groups of series and complex circuitsThen find equivalent resistances of each groupThen work backwards to determine potential difference and currentMrs. Cockrell sample problem
18ExampleA circuit is assembled such that a 6 ohm and 2 ohm in series with each other is in parallel with a 4 ohm resistor. This entire group is in series with a 3 ohm resistor and a 6 ohm resistor. Following the series/parallel group is a 1 ohm resistor. All attached to a 9V battery. Determine the current in and potential difference across the 2 ohm resistor.
19Power The rate at which energy is transferred. Example: P=IV P = Power (W)I = Current (A)V = Electric Potential (V)Example:A 6.0V battery delivers a 0.50 A current to an electric motor that is connected across its terminals. (A) what is the power of the motor? (B) If the motor runs for 5.0 minutes, how much energy is delivered?