1. J. Gabrielse Ohm’s law V I R

2. J. Gabrielse Voltage (V) Definition: what pushes charges Unit: volt (V) Measured by putting voltmeter in parallel. -+

3. J. Gabrielse Current (I) Definition: moving electrical charge Unit: ampere (A)  sometimes called Amps Measured by putting ammeter in series. Why?  So the current has to run through the meter. -+

4. J. Gabrielse Resistance (R) Definition: how hard it is for charges to move Unit: ohm (Ω) Measured by putting multimeter in parallel. Disconnect all batteries. The multimeter shows the resistance between the two points you touch.

5. J. Gabrielse ? I R I R Ohm’s Law: V = I R V I R V = I = R = ? ? What is the equation for V?

6. J. Gabrielse VRVR ? I R I R Ohm’s Law: V = I R V I R V = I = R = ? What is the equation for I? ?

7. J. Gabrielse VRVR ? I R I R VIVI Ohm’s Law: V = I R V I R V = I = R = What is the equation for R? ?

8. J. Gabrielse R equivalent = R A + R B Resistors in Series -+ RARA RBRB = -+ R equivalent What is the resistance of the circuit? We can replace R A and R B with an equivalent resistor, R equivalent.

9. J. Gabrielse R equivalent R equivalent = 50 Ω Resistors in Series Example -+ 30 Ω20 Ω = -+ R equivalent = R A + R B = 30Ω + 20Ω = 50Ω

10. J. Gabrielse Resistors in Parallel -+ RARA RBRB = -+ R equivalent  In parallel circuits we can also replace R A and R B with one equivalent resistor, R equivalent. J. Gabrielse

11. What is R equivalent ? Resistors in Parallel Example -+ = -+ R equivalent 30 Ω 20 Ω J. Gabrielse

12. Notes

13. J. Gabrielse Your Turn: Practice Problems p. 515: 5, 6, 7 Questions?  Come see me. Get your class work grade before you leave.