1. Electric Current and Electrical Energy
Chapter 17, Section 2

2. Electric Current
Electric current is the rate at which electric charges flow (electricity).
The unit of current is the amp (A or I).
The higher the current, the greater the number of charges that pass the point each second.
A. Making Charges Move
Do charges in a battery instantly reach a light bulb? NO!
The electric field causes the free electrons in the wire to move. The energy of each electron is transferred instantly to the next electron.
Commanding Electrons to Move
This electric field is created so quickly that all electrons start moving through the wire at the same instant.

3. AC and DC
In direct current, the charges always flow in the same direction.
In alternating current, the charges continually shift from flowing in one direction to flowing in the reverse direction.

4. Voltage
Voltage is the potential energy difference between two points in a circuit.
The unit for voltage is the volt (V). Voltage
Voltage causes current to flow through an electric circuit.
Voltage and Energy
The higher the voltage, the more energy is released per charge.
Voltage and Electric Current
The greater the voltage, the greater the current.
A greater current means that more charges move in the wire

5. Resistance Paths of Least Resistance
Current depends on more than just voltage.
Current also depends on resistance.
Resistance is the opposition to the flow of electric charge.
The unit of resistance is the ohm (Ω).
The greater the resistance, the less current there is for a given voltage.
Thick wire = less resistance
Thin wire = more resistance
Better conductors = less resistance
Higher temperatures = more resistance
Paths of Least Resistance
Electrons take the path of least resistance -- remember - electrons are lazy! If two paths are available, they will flow through the one with less resistance.

6. Good conductors have low resistance, while insulators have high resistance.
Resistance increases as temperature increases.
Superconductors are materials where the resistance is 0 ohms because it is so cold.