ELECTRICAL CIRCUITS ELECTRIC CURRENT Electric current is the

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. 3

DRAWING CIRCUITS CIRCUIT DIAGRAM SYMBOLS • Circuits can be represented using schematic diagrams with agreed-upon symbols.

SIMPLE CIRCUIT • 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 Resistor Voltmeter

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 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.

SERIES CIRCUITS • In a series circuit, all components (e. g. , dry cells, wires, light bulbs) are connected end-to-end, forming a single path for electrons. A Series Circuit • 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. PARALLEL SERIES 3. 4. A PARALLEL SERIES A

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 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 • In each diagram, is the ammeter hooked up correctly to these circuits? A A A

CONNECTING A VOLTMETER • In each diagram, is the voltmeter hooked up correctly to these circuits? V V 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