The Lead Acid Electric Battery

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The Lead Acid Electric Battery
Sulfuric Acid Electrolyte
-

Terminals
Oxidation at the Negative Plate (ElectrodeAnode)
Sulfuric Acid Solution H2SO4
Spongy Lead (Pb)
Lead Oxide (PbO2)
Reduction at the Positive Plate
(ElectrodeCathode)
Cell 2 V Battery Multiple cells
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Batteries
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Kirchoffs Rules

• Conservation of charge
• Junction (Node) Rule At any junction point, the
  sum of all currents entering the junction must
  equal the sum of the currents leaving the
  junction.
• Conservation of energy
• Loop Rule The some of the changes in potential
  around any closed path of a circuit must be zero.

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Energy in a circuit
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Series Circuit
Apply the Loop Rule

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Parallel Circuits

Apply the Junction Rule
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Rule Set Problem Solving Strategy

• A resistor transversed in the direction of
  assumed current is a negative voltage (potential
  drop)
• A resistors transversed in the opposite direction
  of assumed current is a positive voltage
  (potential rise)
• A battery transversed from to is a positive
  voltage.
• A battery transversed from to - is a negative
  voltage.
• Ohms Law applies for resistors.
• Both the loop rule and junction rule are normally
  required to solve problems.

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More about the Loop Rule

• Traveling around the loop from a to b
• In (a), the resistor is traversed in the
  direction of the current, the potential across
  the resistor is IR
• In (b), the resistor is traversed in the
  direction opposite of the current, the potential
  across the resistor is is IR

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Loop Rule, final

• In (c), the source of emf is traversed in the
  direction of the emf (from to ), and the
  change in the electric potential is e
• In (d), the source of emf is traversed in the
  direction opposite of the emf (from to -), and
  the change in the electric potential is -e

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Example Problem 1
Given
V 3 Volts
Find current in each resistor
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Example Problem 2
Given
Find current in the 20 W resistor
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Alternating Current
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AC Power
?
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Root Mean Square (rms)
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The Wheatstone bridgea simple Ohmmeter
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Charging a capacitor in an RC circuit
Same Symbol
At t 0, Qo 0 and
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Solving the charging differential equation
Kirchoffs loop rule
Convert to a simple equation in Current by taking
the first derivative w.r.t. time
Separate variables
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Integrate the results
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Charge buildup
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Discharging the capacitor in an RC circuit
At t 0, Q Qo
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Solving the discharging differential equation
Kirchoffs loop rule
Separate variables
Integrate
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Charge and current decay
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Charge and current decay
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Electrical Safety

• Current kills, not voltage (70 mA)
• Normal body resistance 105 W
• But could be less than 1000 W
• Take advantage of insulators, remove conductors
• Work with one hand at a time
• Shipboard is more dangerous
• Electrical safety is an officer responsibility