1. More fun with circuits!

2. Warmup Question A 120 v power source is used to power a 15 Ω toaster.
Draw a circuit to represent this situation.
What is the current intensity?
Is this deadly?
Warmup Question

3. Warmup Question A 120 v power source is used to power a 15 Ω toaster.
Draw a circuit to represent this situation.
What is the current intensity?
Is this deadly?
Warmup Question

4. Draw the schematic version of this circuit
Draw the schematic version of this circuit. Which way does the current go?

5. For many circuits, you will see the letter I next to an arrow showing the current direction through the wire.
This is referred to as ”conventional current” and it always goes from the + end of the power source to the – end.
Current Direction I

6. Wrong! Current Direction
For many circuits, you will see the letter I next to an arrow showing the current direction through the wire.
This is referred to as ”conventional current” and it always goes from the + end of the power source to the – end.
Current Direction
Wrong! I

7. Why is this wrong?
Current Direction I

8. In reality, the electrons move toward the positive terminal (opposites attract!)
So conventional current and the actual flow of electrons is in the opposite direction.
Even though it is backwards from the actual direction of electron movement, we’ll mostly use conventional current to help us figure out some aspects of circuits.
Current direction

9. Types of Electric circuits
There are two types of electric circuits to know.
SERIES CIRCUITS
All devices are connected in one continuous loop.
Types of Electric circuits

10. 2. PARALLEL CIRCUITS
The current branches off at least once, and the current splits up to go down each path.

11. Draw a series circuit with a power source, and 3 resistors, R1, R2 and R3.
Draw a parallel circuit with a power source and 3 resistors, R1, R2 and R3. Each resistor must have its own branch.

12. PREVIOUS EXAM QUESTION: Which is better? Series or parallel?
It depends on the situation, but there is one major advantage to parallel circuits…
PREVIOUS EXAM QUESTION: Which is better? Series or parallel?

13. PREVIOUS EXAM QUESTION: Which is better? Series or parallel?
It depends on the situation, but there is one major advantage to parallel circuits…
PREVIOUS EXAM QUESTION: Which is better? Series or parallel?

14. PREVIOUS EXAM QUESTION: Which is better? Series or parallel?
If a resistor burns up in a series circuit, the entire circuit will go dead because the only path for electrons has been interrupted.
If a resistor burns up in a parallel circuit, only the resistor(s) on that branch will go dead because there are other paths for the electrons to take.

15. Well now you don’t have to
Well now you don’t have to! Just use an ammeter (measures current) and a voltmeter (measures potential difference)
Feeling lazy and don’t want to calculate voltage and current intensity?

16. Very important… Ammeters MUST be connected in series.
Voltmeters MUST be connected in parallel.
Very important…

17. Draw a series circuit with power supply, lamp, and motor
Draw a series circuit with power supply, lamp, and motor. There must be an ammeter and a voltmeter to measure the potential difference of the motor.
Series example

18. Draw a parallel circuit with a power supply and 3 resistors (R1, R2 and R3) that are each on separate branches. Include a voltmeter for R2 and an ammeter to measure the current across R1 and R3.
Parallel example: