1. Resistors in Series or in Parallel Chapter 20 Section 2

2. Single Resistor Alone In a circuit that consist of single bulb and a battery, the potential difference across the bulb equals the terminal voltage. In a circuit that consist of single bulb and a battery, the potential difference across the bulb equals the terminal voltage. The current can be found using Ohm’s Law if the resistance is known. The current can be found using Ohm’s Law if the resistance is known.

3. Series Series – Describes a circuit or portion of a circuit that provides a single conducting path without junctions. Series – Describes a circuit or portion of a circuit that provides a single conducting path without junctions. Charges that pass through one resistor must pass through the second resistor and then the third and so on. Charges that pass through one resistor must pass through the second resistor and then the third and so on. All charges follow the same path then it is said to be connected in series. All charges follow the same path then it is said to be connected in series.

4. Series Circuit Diagram

5. Conservation of Charge According to conservation of charge, the amount of charge that enters a resistor must equal the amount of charge leaving the resistor. According to conservation of charge, the amount of charge that enters a resistor must equal the amount of charge leaving the resistor. Resistors that are connected in series, the current in each resistor is the same. Resistors that are connected in series, the current in each resistor is the same.

6. Total Resistance Equivalent Resistance – The total resistance of the circuit. Equivalent Resistance – The total resistance of the circuit. The equivalent resistance in a series circuit is the sum of the circuits resistance. The equivalent resistance in a series circuit is the sum of the circuits resistance. The equivalent resistance can then be used to find the current in the circuit as long as the voltage is known. The equivalent resistance can then be used to find the current in the circuit as long as the voltage is known.

7. Resistors in Series Equation

8. Potential Difference Across Resistors The potential difference across each resistor is different. The potential difference across each resistor is different. The current across each resistor is constant. The current across each resistor is constant. V 1 = IR 1 V 2 = IR 2 V 3 = IR 3

9. Why Use Series Circuits? Resistors placed in series can regulate the current in a device. Resistors placed in series can regulate the current in a device. Lots of resistors will make the current very low. Lots of resistors will make the current very low. This is why Christmas lights are in series so the filament doesn’t have to withstand high currents which could cause fires. This is why Christmas lights are in series so the filament doesn’t have to withstand high currents which could cause fires. Several lesser resistors can make one large equivalent resistor which may not be available. Several lesser resistors can make one large equivalent resistor which may not be available.

10. Parallel Circuits Parallel – Describes two or more components in a circuit that are connected across common points or junctions, providing separate conducting paths for the current. Parallel – Describes two or more components in a circuit that are connected across common points or junctions, providing separate conducting paths for the current. The advantage to parallel circuits is that if one of the lights on a strained go out, the rest of the lights remain lit. The advantage to parallel circuits is that if one of the lights on a strained go out, the rest of the lights remain lit.

11. Parallel Circuit Diagram

12. Resistors In Parallel & Voltage Resistors in parallel have the same potential difference across them. Resistors in parallel have the same potential difference across them. The current across the resistors vary on the strength of resistance. The current across the resistors vary on the strength of resistance.

13. Resistors in Parallel Equation

14. Resistors in Series or in Parallel Circuit TypeSeriesParallel Schematic Diagram Current Potential Difference (Voltage) Equivalent Resistance