1. Resistance

3. What is resistance? Resistance is the amount that a material holds back the flow of electrons Atomic nuclei (plural of nucleus) get in the way of moving electrons Similar to the idea of friction

4. What is resistance? Resistance causes electrons to use some of their energy to move through the wire – there is a potential difference

5. What is resistance? Measured in units called Ohms (Ώ) – named after German physicist Georg Ohm (1789 – 1854)

6. Ohm’s Law Ohm noticed the relationship between voltage and current in electrical circuits (Ohm’s Law) V = I x R

7. What a waste! Energy lost to a resistor is converted to heat and/or light We can use the resistance of materials to our advantage

8. What a waste! For example, light bulb filaments are made out of Tungsten

9. What a waste! The longer an extension cord or speaker wire is, the more resistance it has Reduced sound/light efficiency

10. Food for thought What happens to current and voltage in an electrical circuit if we increase resistance?