Electrical Circuits

Electric Current Electric current: is the orderly flow of electrons through a conductor. Electron flow: the direction the electrons move in a circuit from the negative terminal to the positive terminal (- to +). Conventional current: the direction positive particles would flow if they could move in a circuit from the positive terminal to the negative terminal (+ to -). Note most circuits are calculated using conventional current. Electric circuit: is a continuous path for electricity to flow through.

CORE CONCEPTS Circuits can be: created and represented using schematic diagrams. measured in terms of their properties, including voltage and current. Safety is a key consideration when near current electricity.

DRAWING CIRCUITS Circuit Diagram Symbols Circuits can be represented using schematic diagrams with agreed-upon symbols.

SIMPLE CIRCUIT The three main parts of an electric circuit are: A Simple Circuit The three main parts of an electric circuit are: energy source – this can be a battery, an outlet, or something that creates electrical power load – is where electrical power is converted into something else; light bulb, fan, hair dryer, stove etc… conducting material – material that conducts electricity, like a metal wire. A switch and other components can be added. Various instruments can be used to measure the circuit’s properties.

Simple Circuits Power Supply Ammeter - + A v Voltmeter Resistor

MEASURING CIRCUITS I Circuits can be measured in terms of their properties, most notably voltage and current. Voltage The electric potential difference in a circuit. Measured in volts (V), the amount of electric potential energy in every coulomb of charge. Our homes typically have 120 V electrical systems. Simple Circuit (with Voltmeter) We use a voltmeter to measure voltage. Voltmeters are always attached in parallel (making a second branch in the circuit).

MEASURING CIRCUITS II Current the amount of charge that passes a point in a circuit in a given time. measured in amperes (A) typical current in: a light bulb – 1 A or less a TV – 3 A a car battery – 500 A Simple Circuit (with Ammeter) We use an ammeter to measure current. Ammeters are always attached in series (in a row / in a single path).

CORE CONCEPTS There are two main kinds of circuits: Series and Parallel. Series and parallel circuits can be distinguished by their structure. Series and parallel circuits can be distinguished by their properties. We use an ammeter to measure current and a voltmeter to measure voltage in a circuit. Note: Students and other scientists don’t always achieve perfect results measuring series and parallel circuits. Parallel Series

SERIES CIRCUITS A Series Circuit In a series circuit, all components (e.g., dry cells, wires, light bulbs) are connected end-to-end, forming a single path for electrons. Current only follows one path and must pass through each of the components. If one part of the circuit is broken, the entire circuit will stop functioning.

PARALLEL CIRCUITS In a parallel circuit, there is more than one path for electric current. A “branch” in a parallel circuit is made by forming junction points for the current to split up and rejoin. If part of the circuit is defective/broken, another part may still be able to operate. A Parallel Circuit

Example #1 Identify if each circuit is in series or parallel? 2. 1. 3. 4. SERIES PARALLEL

Adding an Ammeter into a Circuit In order to measure the current traveling through a circuit, an ammeter must be inserted into the circuit. An ammeter is always connected inside the circuit. A

Adding a Voltmeter to a Circuit In order to measure the voltage traveling through a circuit, a voltmeter must be inserted into the circuit. A voltmeter is always connected outside the circuit. V

MEASURING SERIES vs. PARALLEL CIRCUITS Series Circuits Current: is unaffected (it has one path). Voltage changes: Loads (or resistors) placed in series decrease voltage. Power sources placed in series increase voltage. In a series circuit, the current remains the same, but the voltage changes.

MEASURING SERIES vs. PARALLEL CIRCUITS Voltage is unaffected; it stays constant through all branches. Current changes; it must split into the branches of the circuit. In a parallel circuit, the voltage remains the same, but the current changes.

Connecting An Ammeter A) B) C) NO YES YES F) E) D) NO YES NO In each diagram, is the ammeter hooked up correctly to these circuits? A) B) C) A A NO A YES YES F) E) D) NO A YES NO A A

Connecting A Voltmeter In each diagram, is the voltmeter hooked up correctly to these circuits? V A) B) C) V V NO YES YES F) E) D) V YES V YES NO V

Setting up a Circuit PARV acronym P-ower A-mmeter R-esistor V-olt Meter

Assignment Page 305, Q’s 1 – 7, 11, 12 Page 309, Q’s 3 - 10