Electromotive Force

parts of an automobile or different parts of the electricity in one’s home. It is the case with circuit breakers, for example. Each resistor will have the full voltage.

Because of the conservation of charge, the current will be the sum of the different currents through each resistor. According to this, the inverse of the total resistance is equal to the sum of the inverses of the resistances, which is similar to capacitors. This means that the resistance in total will be less than the smallest of the individual resistances, increasing the total current to the resistors. Parallel resistors do not each get the total current; they divide it.

In some circuits, there are resistors in parallel and in series. Wire resistance itself is in series, while other resistances are considered to be in parallel. There is a certain resistance that is gotten from the wires themselves that must be one resistance calculated. This must be added to the resistances of those resistors in parallel. In some cases, the wire resistance is negligible but, in other cases, the wire resistance cannot be negated. With worn or long extension cords, the resistance in the wire might be great, reducing the voltages available to the different plug-ins.

ELECTROMOTIVE FORCE

There are many different types of voltage sources, including many different types of voltages. There is wind energy, nuclear energy, and solar energy. Each of these will create a potential difference and can supply a current. The potential difference will create an electric field that causes this current. This is referred to as electromotive force, even though it isn’t a force at all. Instead, it is a certain type of potential difference in electricity. The units of EMF are volts, which is the potential difference of a source when no current is flowing. The EMF will decline as the battery is depleted. The output voltage is referred to as the EMF.

A larger truck battery that is twelve volts can deliver more current than a 12-volt motorcycle battery. The EMF is the same with both of them but, because of size, there is a smaller internal resistance called r in the larger battery. The internal resistance will block the flow of current from within the source. As a battery is depleted, the internal resistance will increase but it is more complex than that. For example, the internal

resistance of rechargeable nickel-cadmium cells, depends on how many times and how significantly the batteries have been depleted.

The voltage output of a device is measured by measuring the potential difference across its terminals. This is called the terminal voltage. It consists of the EMF minus the current and internal resistance multiplied by each other. This means that, if the current is high or the internal resistance is high, the terminal voltage will be decreased. If the internal resistance becomes significant, the terminal voltage will be diminished, which is the case when the battery dies down.

Battery testers will actually test internal resistance. Because they use small load resistors to intentionally draw a current from the battery, they check to see if the terminal voltage has dropped below an acceptable level. If the battery is weakening, the internal resistance will be high and the terminal voltage will be low. Battery chargers will pass a current opposite to the current they supply. The voltage output of the battery charge must be greater than the EMF of the battery in order to reverse the current going through it. It replenishes its chemical potential.

Batteries for toys and flashlights are set up in series in order to produce a larger total EMF. They must be put in the right order or the total EMF, which is the sum of the EMFs of each battery, will not add up and the batteries will not work. The disadvantage is, however, that their internal resistances will add up. This makes a series of batteries less effective than one larger battery even though their EMFs will be the same as a larger battery.