#### Transcript 20.2 Electric Current and Ohm’s Law

```Warm-Up 12/19/13
• Draw a 3 frame cartoon strip that shows the
series of events that may cause you to receive a
shock from a metal door knob on a dry winter
day.
20.2 Electric Current and Ohm’s
Law
Thursday 12/19/13
Electric Current
• A continuous flow of electric charge
• Measured in Amperes/Amps (A)
• There are two main types:
▫ Direct Current (DC)
▫ Alternating Current (AC)
DC
AC
• Charge flows only in
one direction
• Example: flashlight or
battery operated
device
• Flow of electrical
charge that changes
direction
• Example: electricity
in home and school
Voltage
• Also known as the “potential difference”
• The difference in electrical potential energy
between two places in an electric field
▫ CHARGE FLOWS FROM AREAS OF HIGH TO
LOW CHARGE
• Sources of voltage: batteries, solar cells,
generators
Conductors & Insulators
• Different types of materials are better at
supporting an electric current
• Conductors: charge can flow easily, like in
metal wires
• Insulators: charge can’t flow
easily, like through plastic or rubber
Resistance
• Measures the opposition or difficulty of charge
flow in a material
• Unit is Ohms
• Low resistance materials are
▫ THIN, SHORT, AND COLD
• High resistance materials are
▫ THICK, LONG, AND HOT
Ohm’s Law
• Shows the relationship between voltage, current,
and resistance.
V=IxR
Voltage (Volts) = Current(Amps)x Resistance (Ohms)
• You can increase voltage by increasing current
or resistance
Your Job
• Complete the Ohm’s Law practice problems.
```