Matter & Energy


Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Series and Parallel Sources

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Sources of electric current can also be connected in various ways. Sources can be arranged in series by connecting a terminal of one source to the opposite terminal of the next source. For example, if the positive terminal of battery A is connected to the negative terminal of battery B, and the positive terminal of battery B to the negative terminal of battery C, then batteries A, B, and C are in series. The load is then placed between the positive terminal of battery C and the negative terminal of battery A.

When sources of electric current are connected in series, their total voltage is equal to the sum of their individual voltages. For example, three 1.5-volt batteries connected in series furnish a total of 4.5 volts. If the load is 9 ohms, the batteries send a current of 4.5/9 = 0.5 amp through the load.

Current sources may be arranged in parallel by connecting all the positive terminals together and all the negative terminals together. The load is then placed between the group of positive terminals and the group of negative terminals.

Arranging sources in parallel does not increase the voltage. If three 1.5-volt batteries are connected in parallel, the total voltage is still 1.5 volts. Batteries should not be connected in parallel unless they have approximately the same voltage. If a high voltage battery is connected in parallel with a low voltage battery, the high voltage battery will force an electric current through the low voltage battery and damage it.