Electrical Resistance and Ohm’s Law
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Learning Objective
In this lesson we will learn about electrical resistance and how it can be calculated.
Learning Outcomes
By the end of this lesson you will be able to:
- Define electrical resistance and give examples of materials with high and low resistance.
- Describe how different factors can affect the resistance of an electrical wire.
- Describe fixed and variable resistors.
- Calculate total resistance in series and parallel circuits.
- Use Ohm’s law to calculate resistance, voltage and current.
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Lesson Summary
- Resistance is a measure of the restriction of current flow.
- It is measured in ohms (Ω).
- Conductors have low resistance and readily conduct electricity.
- Semiconductors have some resistance but still conduct electricity.
- Insulators have very high resistance and do not conduct electricity.
- The resistance of an electrical wire depends on:
- The type of metal
- The purity of the metal
- The length of the wire
- The thickness of the wire
- Resistors are electrical components designed to reduce current.
- Fixed resistors have a set level of resistance.
- Variable resistors have an adjustable level of resistance.
- The total resistance in a series circuit is calculated using the formula:
- The total resistance in a parallel circuit is calculated using the formula:
- Ohm’s law states that the mathematical relationship between resistance, voltage and current is given by the formula:
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(Header image: Igor Batenev, Adobe Stock)