1. Ohm’s Law PSSA Requirement Unit 9 Honors Physics

2. A look at electricity Static Electricity Charges are stationary (mostly) Look at force between charges Electric field around charged particles Potential from a charged particle Current Electricity Charges are moving (flowing) Look at how circuits work Resistance to the flow

3. A New Language Quantities –Current (unit - Amperes (A) –Voltage (unit - Volt (V)) –Resistance (unit - Ohms (Ω)) Option - Z gives Ω Symbol

4. Electric Current Current is defined as the rate at which charge flows past a given point Unit of Current: A (ampere) = C / s

5. Current and Flow Either positive or negative particles can flow Conventional Current - direction positive charge would flow

6. Microscopic View of Current

7. Circuit Requirements Circuit - complete path of conductors for electrons (closed loop) Battery - Power Source - pushes electrons around Something to use the current - light bulb Switch

8. Circuits

9. Measuring Current and Voltage Ammeter - measures current –Must be placed in series (in line) with object it is measuring Voltmeter - measures potential difference between two points in a circuit –Must be placed in parallel (around) the object it is measuring Multimeter - Can measure more than 1 quantity

10. Voltage and Current When a voltage is applied to a conductor - current is proportional to the applied voltage Proportionality Constant is called Resistance

11. Resistance / Ohm’s Law Units - Ω (ohms)

12. Ohm’s Law Notes Georg Simon Ohm (1787 - 1854) studied electrical resistance ∆V = I R ∆V is the potential drop across the resistor Ohm’s Law is only valid for certain materials - ohmic materials

13. Ohmic and Non-Ohmic Materials

14. Ohm’s Law Problems An iron carries a current of 6.4 A when connected to a 120 V source. What is the resistance of the steam iron?