Batteries. The chemical reactions in this cell may be approximated by Some of the complexity of this reaction comes from the fact that the reduction of the ammonium ion produces two gaseous products 2NH4+(aq) + 2e- -> 2NH3(g) + H2(g) which must be absorbed to prevent the buildup of gas pressure. That is accomplished with two further reactions in the paste electrolyte. ZnCl2(aq) + 2NH3(g) -> Zn(NH3)2Cl2(s) 2MnO2(s) + H2(g) -> Mn2O3(s) + H2O(l) The voltage of this cell is initially about 1.5 volts, but decreases as energy is taken from the cell. Battery with internal resistance. Electricity Generation and Distribution. Automobile Battery Example. Household Electric Circuits. Breakers and Ground Wires. Ground Fault Interrupter. GFI's are required by the electrical code for receptacles in bathrooms, some kitchen receptacles, some outside receptacles, and receptacles near swimming pools. The horror story scenarios which led to these code requirements are things like dropping a hair dryer or a portable radio into a bathtub with a person, causing electrocution.
A typical circuit breaker interrupts the ciruit at 20 amperes, but it takes only about 100 milliamperes to electrocute a person in such a scenario. The GFI is designed to detect currents of a few milliamperes and trip a breaker at the receptacle or at the breaker panel to remove the shock hazard. The GFI has a "Test" button which causes a small difference between "hot" and neutral currents to test the device. Electric Shock Hazards.