Solve for Z ABCDE STVX HKMNP WYZ Chapter
Solve for Z ABCDE STVX = HKMNP WYZ
Chapter 22 Current Electricity
Electric Current • The flow of charged particles
Circuit • Closed loop through which charged particles flow
Voltaic Cell • Converts chemical energy into electrical energy
Battery • Several cells connected together
Photovoltaic Cell • Changes light energy to electrical energy
Charge Pump • Increases potential energy of the charges
Charge Pumps • Batteries, generators, voltaic cells
Electricity Units Watt (W) = J/s Ampere (A) = C/s Resistance (R) = V/C Voltage (V) = J/C
Current (I) • Electric flow in coulombs per second
Conventional Current The flow of positive charges
Electric Power • Product of potential difference & current
Power (P) P = VI
Resistance (R) • Ratio of potential drop to current flow
Resistance (R) unit = ohm (W)
Resistance (R) V R = I
Rearranged V = IR
Resistor • A device designed to have a specific resistance
Resistor • Made of thin wires, graphite, semiconductors, etc
Resistors • Light bulb, toaster, etc
Current can be changed by varying either voltage or resistance
Potentiometer • Variable resistor • rheostat
Schematic • Diagram of electric symbols for components in a circuit
Electric Symbols On page 454
Conductor
Switch
Fuse
Capacitor
Resistor (fixed)
Potentiometer
Ground
Battery
Lamp
Voltmeter V Measures Potential Difference or volts
Voltmeter V Must be connected in parallel with circuit
Ammeter A Measures current or amps
Ammeter A Must be connected in series with the circuit
DC Generator
Electric Connection
No Electric Connection
When a capacitor is charged through a resistor, the current is high, but falls quickly
Power dissipated (used up) in a resistor is proportional to the resistance
Power dissipated in a resistor is proportional to the current squared
Power Formula P = 2 IR
The total electrical energy transferred equals the power times the time
Energy Formula E = 2 I Rt
Energy = power x time is measured in kilowatt hours
F o r m u l a s P V P E = = VI IR 2 I Rt
A current of 0. 50 A passes through a 120 V outlet for 5. 0 minutes: Calculate: P, R, & E
A 60. 0 W light is connected to a 120 V outlet for 2. 5 hours: Calculate: I, R, & E
Headlights burn for 7. 5 hrs with a resistance of 48 W in a 12 V system Calculate: I, P, & E
- Slides: 52
