Solve for Z

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Chapter 22Current

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 UnitsWatt (W) = J/s

Ampere (A) = C/sResistance (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 ()

Resistance (R)

R = V 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 = I2R

The total electrical energy transferred equals the power

times the time

Energy Formula

E = I2Rt

EnergyEnergy = power x time is measured in kilowatt hours

Formulas

P = VIV = IRP = I2RE = I2Rt

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 in a 12 V system

Calculate: I, P, & E