The Flow of Electricity
1. Give examples of voltage sources that can maintain a potential difference in a circuit..
2. Distinguish between AC and DC.
3. Describe the structure and uses of dry cells and wet cells.
voltage source alternating current direct current dry cell wet cell thermocouple
symbol for current is I
of measurement is the ampere (A) or amp
symbol is R
unit of resistance is the ohm (W)
The symbol is V
The symbol is V
The unit of voltage is the volt
= voltage / resistance
= volts / ohms
Everybody knows that in order for a electrical device to work it needs a power source with enough energy to power the device. More exactly there needs to be enough potential difference (voltage) in the source to power the device. One type of voltage source is the electrochemical cell.
a steady electric current from chemical energy.
dry cell consists
of a zinc can, electrolyte paste, and a carbon rod in the center.
chemical reaction takes place between the zinc can and the paste.
flow from the negative (zinc) terminal to the positive (carbon) terminal
are then pumped back to the negative terminal
difference in the amount of electrons at the terminals creates electron
pressure or what is called an electrochemical gradient.
of dry cells connected to one another is called a battery.
called a voltaic cell and is another type of electrochemical cell.
Consists of an electrolyte solution, a zinc rod, and a copper rod,
is broken down to release electrons in the electrolyte solution (H2SO4)
excess electrons then flow from the negative terminal (zinc) to the positive
terminal (copper) and then back through the electrolyte solution to the zinc
this is driven by electron pressure
used as car batteries
a device that changes heat energy into electrical energy.
of a heat source,
a copper wire,
an iron wire
a cold source.
electricity as a result of temperature differences
greater the temperature difference, the greater the electrical current.
thermostats in cars, heaters and ovens.
current flows in one direction it is called DC (direct current)
are dry cells, wet cells, and thermocouples.
current flows in both directions it is called AC (alternating current)
Nearly all industry runs on AC (An example is the current in your home)
110-120V home & 220-240V industry, foreign countries and large applications (oven, air conditioning)
Made in large electric generators
Generators in America alternate charge at 60Hz (cycles/sec)