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Ohm's Law: Resistance and Simple Circuits by nayeli morales

Ohm's law variables:

  • R- resistance (upper case Greek omega)
  • V- voltage (volts)
  • I- electric current (ampere)

Vocabulary:

  • Resistance- (R) An electric property that delays current.
  • Ohmic- substances that work with Ohm’s law. (Non ohmic) do not work with the law.
  • Simple circuit- Has only one voltage source and resistor.

Ohm’s law- Is that the current that flows through most substances are the same. George Simon Ohm, was a German physicist who first showed that the current in a metal wire was relative to the voltage applied. We can view this as a cause and effect relationship. Voltage being the cause and current being the effect. His law is not universally valid.

Resistance is the electrical property that delays current. It’s the moving charges crashing into atoms and molecules in something which transfers the energy to it limiting current. Resistence is opposite proportionally to current. Resistance is related to the shape and material of an object, which will be seen in Resistance and Resistivity. If resistence doubles current is then cut in half. Putting together voltage to current and current to resistence give I=V/R.

Ohmic materials and non-ohmic materials

(No need to go in depth in this) The many substances that uphold to Ohm’s law are called ohmic, and the ones that don’t are non-ohmic. Ohmic includes good conductors and some poor conductors. Ohmic materials include a resistance that is unaided by voltage and current. Objects with simple resistance are called resistors. Switching I=V/R gives R=V/I, so the units of resistance are 1ohm=1volt per ampere. Which is also 1(omega)=1(V/A).

A simple circuit

A simple circuit has one voltage source and one resistor. The wires connecting the two can be negligible, or their resistance can be included with R.

The zigzag represents the one resistor. The parallel lines represent a battery.

Conceptional questions:

  • The IR drop across a resistor means that there is a change in potential or voltage across the resistor. Is there any change in current as it passes through a resistor? Explain. No, because current is directly proportional to the voltage.
  • How is the IR drop in a resistor similar to the pressure drop in a fluid flowing through a pipe? The voltage source is like a pump, which is creating a pressure difference that causes current flow of charge. The resistor is like a pipe that is reducing the pressure and is limiting the flow because of its resistance.

Credits:

Created with images by Nikola Johnny Mirkovic - "untitled image"

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