Electric Current and Electrical Energy

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Electric Current and Electrical Energy

• Chapter 17, Section 2

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• 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.

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• 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

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• 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 (?).
• 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.

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• 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.