Post on 18-May-2015
Electric Current and Ohm’s Law
20-2
Electric Current• A continuous flow of electric charge.• Measured in amps (A) = 1 coulomb per
second• Direct current (DC) when charge flows in
one direction• Alternating current (AC) is a flow of
electric charge that regularly reverses direction.
• EX – home plugs and lights
Electrical Conductors and Insulators
• Conductors are materials through which charge can easily flow– Metals and water
• Insulators are materials through which a charge cannot flow easily.– Wood, plastic, rubber and air
Resistance
• Opposition to the flow of charges in a material
• Measured in ohm.
• A material’s thickness, length, and temperature affect its resistance.
• A thinner, longer and hotter wire increase resistance.
• Superconductor has almost 0 resistance
Voltage• In order for a charge to flow in a wire,
the wire must be connected in a complete loop that includes an energy source.
• Potential difference - difference in potential energy between 2 places in an electric field
• Measured in volts – joules per coulomb
• Batteries convert chemical energy into electrical energy.
Ohm’s Law• Voltage (V), in a circuit equals the
product of the current(I) and the resistance ( R).
• V = I x R or I = V/R
• Increasing voltage increases current. Keeping same voltage and increasing the resistance decreases the current