Question

write down all the physical principles about resistances and currents in simple circuits containing resistors. also write down all the physical principles about resistances and currents in simple ciruits contaning resistors connected in parallel

Answer 1

As the electrons work their way through the thin metal filament of the lamp, they encounter more opposition to motion than they typically would in a thick piece of wire. This opposition to electric current depends on the type of material, its cross-sectional area, and its temperature. It is technically known as resistance. (It can be said that conductors have low resistance and insulators have very high resistance.) This resistance serves to limit the amount of current through the circuit with a given amount of voltage supplied by the battery, as compared with the "short circuit" where we had nothing but a wire joining one end of the voltage source (battery) to the other.

When electrons move against the opposition of resistance, "friction" is generated. Just like mechanical friction, the friction produced by electrons flowing against a resistance manifests itself in the form of heat. The concentrated resistance of a lamp's filament results in a relatively large amount of heat energy dissipated at that filament. This heat energy is enough to cause the filament to glow white-hot, producing light, whereas the wires connecting the lamp to the battery (which have much lower resistance) hardly even get warm while conducting the same amount of current.

As before, with no flow of electrons, the entire potential (voltage) of the battery is available across the break, waiting for the opportunity of a connection to bridge across that break and permit electron flow again. This condition is known as an open circuit, where a break in the continuity of the circuit prevents current throughout. All it takes is a single break in continuity to "open" a circuit. Once any breaks have been connected once again and the continuity of the circuit re-established, it is known as a closed circuit.

Resistance is the measure of opposition to electric current.

A short circuit is an electric circuit offering little or no resistance to the flow of electrons. Short circuits are dangerous with high voltage power sources because the high currents encountered can cause large amounts of heat energy to be released.

An open circuit is one where the continuity has been broken by an interruption in the path for electrons to flow.

A closed circuit is one that is complete, with good continuity throughout.

A device designed to open or close a circuit under controlled conditions is called a switch.
The terms "open" and "closed" refer to switches as well as entire circuits. An open switch is one without continuity: electrons cannot flow through it. A closed switch is one that provides a direct (low resistance) path for electrons to flow through.

Parallel Circuits:
All components share the same (equal) voltage.
Branch currents add to equal total current.
Resistances diminish to equal total resistance.

A parallel circuit is one that has two or more paths for the electricity to flow, the loads are parallel to each other. If the loads in this circuit were light bulbs and one blew out, there is still current flowing to the others because they are still in a direct path from the negative to positive terminals of the battery.

A Parallel circuit has certain characteristics and basic rules:

• A parallel circuit has two or more paths for current to flow through.
• Voltage is the same across each component of the parallel circuit.
• The sum of the currents through each path is equal to the total current that flows from the source.
• You can find total resistance in a Parallel circuit with the following formula:
• 1/Rt = 1/R1 + 1/R2 + 1/R3 +...
• Rt = R (t)otal
• If one of the parallel paths is broken, current will continue to flow in all the other paths.