1. Physics Section 18.2 Apply series and parallel circuits. Note: A simple circuit may contain only one load. A more complex circuit may contain numerous loads. Consider the following series circuit.

2. Properties of series circuits 1. The total resistance (equivalent resistance) of resistors connected in series is the sum of the individual resistors. R t = R 1 + R 2 + R 3 2. The total potential difference in a series circuit is the sum of the potential differences of each source or across each resistor. V t = V 1 + V 2 + V 3 3. The current in a series circuit is constant everywhere.

3. To solve a circuit problem: 1. Find the total resistance. 2. Find the total current. 3. Find the potential difference across each resistor. Example: A 12 V battery is connected to three resistors of 4.0 ohms, 8.0 ohms, and 12 ohms in a series circuit. Find the equivalent resistance and the current in the circuit. Find the potential difference across each resistor.

4. example A 8.0 ohm resistor is connected in series with another resistor and a 12 V battery. The current is 1.2 amps. Find the value of the unknown resistor. Find the potential difference across both resistors.

5. A parallel circuit occurs when two or more components are connected in separate conducting paths connected across a common junction.

6. Properties of a parallel circuit 1. The sum of the currents in each branch of the circuit equals the total current. I t = I 1 + I 2 + I 3 2. The equivalent resistance is less than the smallest resistance. The reciprocal of the total resistance is sum of the reciprocals of each resistor. = + + 3. The potential difference is constant in each branch of the circuit.

7. example A 12 V battery is connected in parallel with resistors of 16 ohms, 20 ohms, and 24 ohms. Find the total resistance, the total current and the current in each branch.

8. example A 15 ohm and a 25 ohm resistor are connected in parallel to battery. A current of.25 amps exists in the 25 ohm resistor. 1. Find the total resistance. 2. Find the potential difference. 3. Find the current in other resistor.

9. Assignment Page 656 Problems 1 - 5