Download R 03/20 Week 10, Chapter 5

Luigi Galvani (1737-1798)
“Animal electricity”
Galvanic Cells
Alessandro Volta showed
that chemical reactions
between metal
electrodes and an
electrolytic fluid can
induce electrical current.
Voltaic Piles and Batteries
Reactions in some
batteries can be
reversed to recharge
the battery.
Dry cell batteries –
“safe” and “portable”
Batteries and Electrical Current
• Electrical current
– Flow of charged particles
– Symbol: I
– Units: Coulombs/second (C/s)
• Voltage
– the difference in electrical charge between two
points in a circuit (electrical “pressure”)
– Symbol: V
– Units: volts (V)
• Battery
– Converts chemical energy to kinetic energy
(energy of flowing charges)
Electric Circuits
• Electric circuit
– Unbroken path of material carrying electricity
– Electrical conductor
• Circuit components
1. Source
2. Closed path
3. Device to use electrical energy
• Ohm’s Law
– Current is directly proportional to voltage V and inversely
proportional to resistance R
– In symbols: I = V / R
• Electric Power: P = I × V
Two Kinds of Electric Circuits