Electric CurrentElectric Current

Chapter 7 section 2Chapter 7 section 2

Electric CurrentElectric Current Electric current-Electric current- The flow of The flow of electronselectrons through a wire through a wire

or any conductor. or any conductor. Measured in units of Measured in units of Amperes (A)Amperes (A)

Charges flow from Charges flow from HighHigh voltage to voltage to LowLow voltage voltage Voltage difference- Voltage difference- pushpush that causes charges to that causes charges to

move- measured in move- measured in volts (V)volts (V) For charges to flow, the wire must always be For charges to flow, the wire must always be

connected in a closed path, or connected in a closed path, or circuitcircuit http://www.school-for-champions.com/science/dc.htmhttp://www.school-for-champions.com/science/dc.htm

ResistanceResistance ResistanceResistance- the tendency for a material to - the tendency for a material to

oppose the flow of electrons, changing oppose the flow of electrons, changing electrical energy into electrical energy into ThermalThermal energy and energy and lightlight

Resistance is measured in Resistance is measured in OhmsOhms ( (ΩΩ)) Making wires thinner, longer, or hotter Making wires thinner, longer, or hotter

increases increases the resistancethe resistance Ohm’s Law- Ohm’s Law- the current in a circuit equals the current in a circuit equals

the voltage difference divided by thethe voltage difference divided by the resistance resistance I = V/RI = V/R

Electrical CircuitsElectrical Circuits

Less resistance means less heat, which is Less resistance means less heat, which is safer for use in your homesafer for use in your home

As resistance increases, current As resistance increases, current decreasesdecreases

As voltage difference increases, current As voltage difference increases, current increasesincreases

Sources of ElectricitySources of Electricity

A A Dry CellDry Cell battery produces a voltage battery produces a voltage difference between its zinc container and difference between its zinc container and its carbon suspension rod, causing current its carbon suspension rod, causing current to flow between them. to flow between them.

Sources of ElectricitySources of Electricity

A A Wet CellWet Cell battery contains two connected plates battery contains two connected plates made of different metals in a conducting solution- made of different metals in a conducting solution- like a car batterylike a car battery

Electrical OutletsElectrical Outlets- have a voltage difference across - have a voltage difference across the two holes of an electrical outlet and a generator the two holes of an electrical outlet and a generator at a power plant provides the voltage differenceat a power plant provides the voltage difference

ResistanceResistance- the tendency for a material to oppose - the tendency for a material to oppose the flow of electrons, changing electrical energy into the flow of electrons, changing electrical energy into ThermalThermal energy and energy and lightlight

Electrical CircuitsElectrical Circuits Series circuit- current has only one path to flow Series circuit- current has only one path to flow

through through Parallel circuit- current has more than one path Parallel circuit- current has more than one path

to flow throughto flow through Magnetic fields form around wires through which Magnetic fields form around wires through which

electricity is movingelectricity is moving Electromagnet- a temporary magnet made by Electromagnet- a temporary magnet made by

placing a piece of iron inside a current-carrying placing a piece of iron inside a current-carrying loop of wire loop of wire More loops = strongerMore loops = stronger More voltage = strongerMore voltage = stronger Only works for DC currentOnly works for DC current