1. CH 5 – Electricity and Magnetism
Electricity Formulas
CH 5 – Electricity and Magnetism

2. How does this all fit together?
The next few slides are ‘enrichment’. They contain topics which are taught and evaluated in the ‘advanced’ science course.
It’s a bit silly to discuss the next few topics without contextualizing the whole of electricity and magnetism so…

3. Static + Mag
Action at a distance

4. Mag Field about a Wire

5. Solenoids What happens if we use a lot of wire?
PhET Generator Simulator
law/latest/faradays-law_en.html

7. Now back to business…

8. What is Electricity?
Electrons flowing through a sample: dynamic electricity
Previously, we discussed static electricity, which is a buildup of electrons on a surface

9. Electrical Circuits
For electricity to flow, there must be a closed electrical circuit
Circuit def’n: movement (flow) of electrons through a closed pathway

10. Describing Electrical Circuits
In order to properly analyze and investigate electrical phenomenon, we must first define certain variables

11. Current Intensity Or just Current
Def’n: # of charges that flow past a given point in an electrical circuit every second
In other words: how many electrons are flowing through the circuit
Symbol: I (capital ‘eye’)
Unit: A
Ampere or ‘amp’ for short
Named for André-Marie Ampère
Specifically A = 1C/s (enrichment)

12. Potential Difference More commonly just called: VOLTAGE
Def’n: Amount of energy transferred between two points in an electrical circuit
In other words: what’s the ‘difference’ between two points on this circuit (not really a good definition)
Actually, the proper definition is a bit more advanced:
Suppose you have a electrical field, the voltage is equal to the work done per unit charge to move the test charge between two points
In other words… suppose you have a field and you want to move an electron from point a to b, the voltage is what you need to do

13. Voltage
Basically…think of voltage, or potential difference, as a difference in terms of electrical circuits
Symbol: V ; Unit: V (volt)
Small voltage High voltage

14. Resistance
Def’n: the ability of a material to hinder (oppose) the flow of electrical current
Symbol: R
Unit: Ω (Ohm)
named for Georg Simon Ohm
Factors that affect resistance:
(we’ll discuss more in detail later)
Nature of substance: conductors, semi-conductors and insulators
Length of wire
Diameter of wire
Temperature: warm elements = more resistancae

15. Ohm’s Law Relates V, I and R V = IR
This formula is given on the formula sheet
Also can be given as 𝑅= 𝑉 𝐼 or 𝐼= 𝑉 𝑅
Again, we’ll discuss more in detail when we get to resistance and conductance, but basically:
For a given resistance, the potential difference in an electrical circuit is directly proportional to the current intensity

16. Ohm’s Law

17. Power
Def’n: The amount of work an electrical device can perform per second
Symbol: P
Unit: W (Watt) = 1 J/s (Joule per second)
In an exam, you will be given
V=IR
P=IV
E=P∆t

18. James Prescott Joule James Watt

19. Electrical Appliances

20. Energy Time Def’n: the ability to do work or affect change Symbol: E
Unit: J (Joule)
Time
Def’n: the total duration of a process
Symbol: t
Unit: s (seconds)
The basic SI unit is the second

21. Formula Manipulation In an exam, you will be given V=IR P=IV E=P∆t
You are not given
E=IV∆t but it is easy to derive… substitute P

22. Unit Conversions
Don’t memorize… understand how to derive

23. Formulas Practice Questions
Now time to practice…