1. Electric Current

2. In this session we will, Review how we measure electric charge Discuss voltage and electric current Look at electric current in batteries Review Ohm’s Law

3. Before we begin, let’s discuss.... How do materials develop electric charge? Under what conditions does electric charge flow?

4. Coulombs Coulomb = standard unit of electric charge In other words, the amount of electric charge possessed by an object is measured in coulombs. One coulomb = 6 billion billion electrons, or about the amount of charge that flows through a 12-watt light bulb. –Shows you how tiny electrons are

5. Coulomb’s Law

6. Volts Voltage exists when there is an imbalance in charge If two objects have different amount of charge, there is voltage between them For example, standard battery has a voltage difference of 1.5 volts between its positive and negative terminals Volts expressed in joules/coulomb

7. Review To This Point In a 12-volt car battery, every coulomb of charge that moves from one side to the other does ________ joules of work.

8. Ohm’s Law Electric current is driven by ________. Electric current is measured in ______, which is dependent on _______ and ______. Electrical resistance is measured in ______. Ohm’s Law: I = V/R, where I is amperes, V is voltage, and R is resistance

9. Ohm’s Law Triangle To calculate voltage, V: put your finger over V, this leaves you with I R, so the equation is V = I × R To calculate current, I: put your finger over I, this leaves you with V over R, so the equation is I = V / R To calculate resistance, R: put your finger over R, this leaves you with V over I, so the equation is R = V / I

10. Ohm’s Law Practice 1) 3 volts is applied over a 6 ohm resistor. What is the current in amperes? 2) A lamp connected to a 6 volt battery passes a current of 0.06 amperes. What is the lamp’s resistance? 3) A 1200 ohm resistor passes a current of 0.2 amperes. What is the voltage?

11. Questions?