WARM UP Two negative charges, one twice as large as the other, are located 0.05 m apart and experience a repulsive force of 5 N. What is the magnitude of the larger charge? How many excess electrons are on the object with less charge.

Physics Honors A/B –Day 3/07/16 & 3/08/16 Electrical currents and Circuits

Agenda Current Voltage Sources Resistors Simple Circuit Build a simple circuit

Create a simple circuit Make a simple circuit with 1 battery, 1 bulb and wires.

Why should we study circuits?

Where is electrical current in real life?

Electrical Current All Electrical circuits have one thing in common They have an Electrical Current Electrical current The amount of charge that flows is a given period of time So what’s flowing?

Electrical Current Flow of current Flow of water analogy

Electrical Current

Example Problem An iphone runs off a current of 0.22 A. How many electrons pass through the iphone in 5 secs?

Voltage Source Voltage Source needed to drive the current through the circuit Two types Direct Current Circuits Constant Current Constant Voltage Alternating Current Circuits Changing Current Changing Voltage

Electric Potential is related to Electric Field

DC Circuit Battery uses chemical reaction to produce a difference in electrical potential between it’s terminals When connected to a circuit, electrons move in a closed path from one terminal through the circuit and back to the other side of battery

Path of Electrons in a Circuit CORRECT Electrons leave from the negative terminal of the battery and return to the positive Path is chaotic and slow like couple of cm/s

Resistance is affected by several factors FactorLower ResistanceHigher Resistance Material Length Area Temperature

Ohms Law

Electric Circuit Symbols Need these symbols to draw schematic of circuit Make this simple circuit then draw a schematic to represent this circuit

Electric Circuit Symbols Build this circuit with 3 lamps and 2 batteries and 3 switches

Voltmeter and Ammeter Voltmeters – measure voltage between any two points in the circuit Connected across the resistor, or device, voltage drop is to be measured Ammeter – measures current through the particular point in the circuit it is connected Connected in the circuit

Electric Circuit Symbols Measure the voltage across the battery Measure the voltage across each of the bulbs Measure the current after each of the bulbs

Electric Circuit Symbols Need these symbols to draw schematic of circuit Build and Design 3 different simple circuits with 3 lamps, switches and batteries On a separate sheet of paper – Turn in the box Draw one version without symbols Redraw with symbols

Semiconductors are the exception to the rule Semiconductors are insulators but when impurities are added they become conductors Doping Depending on impurity, become different kind of conductors N-type have electrons as charge carriers P-type have positive charge carriers called “holes” Temperature increases; resistivity decreases