DO NOW: Calculating current (Make your best guess… We will be learning this today) A series circuit contains a 12-V battery and three bulbs with resistances of 1 W, 2 W, and 3 W. What is the current in amps? Can use as a bell ringer

Unit 4: Electricity Chapter 13: Electrical Systems 13.1 Series Circuits 13.2 Parallel Circuits 13.3 Electrical Power, AC and DC Electricity

13.1 Investigation: Series Circuits Key Question: How can devices be connected in circuits? Objectives: Build and analyze series circuits. Apply an understanding of Ohm’s law to explain their observations. Describe the effects of short circuits.

SWBAT … apply Ohm’s Law to a circuit with multiple light bulbs. Objective Date 1/16/14 SWBAT … apply Ohm’s Law to a circuit with multiple light bulbs.

In in the late 1800s, a major disagreement over the use of AC and DC electricity erupted between two famous inventors. Thomas Edison favored the direct current (DC) method of moving electrical energy from electrical generation stations to homes and buildings. George Westinghouse argued that the alternating current (AC) method worked better. Electrical Systems

Series Circuits In a series circuit, current can only take one path, so the current is the same at all points in the circuit.

Series circuits Inexpensive strings of holiday lights are wired with the bulbs in series. If you remove one of the bulbs from its socket, the whole string of mini bulbs will go out. If the bulb is not removed, the current can travel using the extra wire. However, if a bulb’s filament burns out, but the bulb is still in the socket, the string will stay lighted. How does this work? Mini bulbs have a special backup wire to carry the current when a filament breaks (Figure 13.1). As long as the burned-out bulb is still in the socket, the series circuit will not be broken. The current can travel through the backup wire, called a shunt.

Current and resistance in series circuits If you know the resistance of each device, you can find the total resistance of the circuit by adding up the resistance of each device.

Current and resistance in series circuits Adding resistances is like adding pinches to a water hose. Each pinch adds some resistance. Everything has some resistance, even thin wire.

Energy and series circuits The devices in a circuit convert electrical energy into other forms of energy. Remember * the rate of energy transfer is called power, and is measured in watts (W).

Kirchhoff’s Voltage Law Kirchhoff’s voltage law states that the total of all the voltage drops must add up to the battery’s voltage.

Calculating current A series circuit contains a 12-V battery and three bulbs with resistances of 1 W, 2 W, and 3 W. What is the current in amps? Looking for: …current (amps) Given: …voltage (12V); resistances = 1Ω, 2 Ω, 3 Ω. Relationships: Use: Rtot = R1+R2+R3 and Ohm’s Law I = V ÷ R Solution: Rtot = 6 Ω and I = 12 V ÷ 6 Ω = 2 amps Can use as a bell ringer