1. Why Make Electrons Flow Anyway?
4.2.3A Ohm’s Law & Circuit Basics
By Mr. Wilson
Modified by Mr. Wanninkhof

2. Ohm’s Law Voltage results in current flow More voltage = more current
Resistance opposes current flow
More resistance = less current

3. Example #1
A potential difference of 25.0 volts is supplied to a circuit with 100 ohms of resistance.
How much current flows through this circuit?
I = ?
V = 25 V
R = 100 Ω
electricity
I R = V/I I
IR /R = V /R
I = V/R
I = (25 V) /100 Ω
I = 0.25 A

4. Example #2 A current of 2.0 amperes flows through a 10 ohm resistance.
What voltage must be applied to this resistance?
V = ?
I = 2 A
R = 10 Ω
electricity
I R = V/I I
IR = V
V = (2A)(10 Ω)
V = 20 V

5. Example #3
A 10 volt battery establishes a current of 5.0 amperes in a circuit.
What is the resistance of this circuit?
V = 10 V
I = 5 A
R = ?
electricity
R = V/I
R = (10 V)/(5 A)
R = 2 Ω

6. What is a circuit?
A continuous loop through which current flows from an area of high voltage to a an area of low voltage.

7. Circuit Elements – Voltage Sources
cell
battery

8. Circuit Elements – Resistances
fixed resistor
variable resistor
lamp

9. Circuit Elements – Switch

10. Circuit Elements – Measuring Devices
Measures: VOLTAGE
Resistance: HIGH
Connect to circuit: OUTSIDE
Measures CURRENT
Resistance: LOW
Connect to circuit: INSIDE
voltmeter
ammeter

11. Proper Use of Meters
5 V
2.5 Ω
0 V
2 A
2 A
0 V
5 V
5 V
NEXT

12. End of 4.2.3A