1. Electricity Cont…
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2. Electric current and ohm’s law
Electric Current is the continuous flow of (positive) electric charge.
The unit for current is the Ampere (A) or Amp.
There are two type of current: Direct and Alternating
Direct current (DC) is when the flow of electrons is in only one direction
Alternating Current (AC) is a flow of electric charge that regularly reverses its direction.

3. An electrical conductor is a material through which charge can flow easily. Ex. metals
An electrical insulator is a material through which charge cannot flow easily. Ex. Wood, plastic, rubber, and air

4. Resistance
Resistance is opposition to the flow of charges in a material.
The SI unit for resistance is the ohm (Ω)
Resistance is lower in a thicker wire.
Resistance is lower in a short wire
A metal’s resistance increases with temperature.
A superconductor is a material that has almost zero resistance when it is cooled to low temperatures.

5. Potential difference (Voltage) is the difference in electrical potential energy between two places in an electric field.
The unit for potential difference is Joules/coulomb or Volts
There are three sources of voltage: batteries (converts chemical energy to electrical energy), solar cells, and generators.
Ohm’s Law states the relationship between voltage, current, and resistance.
V (voltage) = I (current) X R (resistance)
Increasing voltage increases current, increasing resistance decreases current

6. Electric Circuits
An electric circuit is a complete path through which charge can flow.
Circuit diagrams use symbols to represent parts of a circuit, including a source of electrical energy and devices that are run by the electrical energy.

7. Switches show places where the circuit can be opened.
An open circuit is on in which the switch is open and the current stops.
A closed circuit is one in which the switch is closed and the current flows.

8. Series circuit
Series circuits are ones in which current has only one path to flow.
If one bulb stops functioning in a series circuit, none of the bulbs can operate.
Ex: christmas lights

9. Parallel circuit
Parallel circuits are circuits with two or more paths through which charges can flow.
If one bulb stops working in a parallel circuit, the rest of the elements still can operate.
Ex: wiring in your house

10. Electrical Power
Electrical Power is the rate at which electrical energy is converted to another form of energy.
P (watts) = I (amps) X V (volts)

11. Examples:
A stereo receiver uses a current of 2.2 amps from a 120 volt line. What is its power?
A television connected to a 120 volt line uses 102 watts of power. How much current flows through it?