introduction 1. current electricity moving charges/electrons current electricity is controlled...

Introduction

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Current ElectricityMoving charges/electrons

Current electricity is controlled movement of charges through a path, usually a conductor of electricity.

Difference between static and current electricity

Examples of static electricity:Examples of current Electricity:

Lightning- static or current?

Measuring Electricity

CircuitsObjectives: To understand

Components of a circuit

Electrical circuit, an electrical network that has a closed loop giving a return path for the

current. Usually consists of source(pusher),

path(conductor) and load(user)

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Components of Electric circuit

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Circuit component

Definition Examples

Electric Source Source of electric energy/current

Battery, Solar cell, Electric generator,

Electric Load anything that uses/absorbs the energy that is being delivered by the electric current in a circuit

Lamps, fan, washing machine, computer,Resistance

Switches A device that connect circuit /allow flow of electrons when “on”

Electronic switches,Mechanical switch

Measuring devices

Measure current, voltage and power

Ammeter,Voltmeter,wattmeter

Symbols(review)

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Activity1) Collect your

activity packet2) Learn how to use

multimeter.• All measuments

only DC in this class

• Only milli Ampere of current measured

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MultimeterHow to connect probes▫Connect red probe into “VΩmA” slot▫Connect the black probe into “COM”How to set the dial to measure the right quantity▫To measure voltage, ▫current and ▫resistanceWhat scale to choose?

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Voltage

Resistance

Activity 1: Voltage 1) Measure voltage of batteries

a) AA b)AAA c)D d)9V2) Swap the connections. What is the voltage? 3)Connect two batteries in series▫What is the voltage?4)Swap one of the batteries at terminals▫What is the voltage?

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Series

▫Connect resistors in series.

ParallelVoltages in parallel

Resistors in parallel

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Voltage and CurrentMeasure current for 1.5V, 100 ohms.Measure current for 1.5V, 1000 ohms.

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Ohm’s law Ohm’s law relates the relation between

voltage and current.As voltage(V) increases, current(I) increases

V=I*R where V is emf/ voltage, I is current, R is resistanceemf is electromotive force

Assumptions: Only for conductors, resistors called “ohmic materials”Materials that do not obey Ohm’s law are called “non-

ohmic” materials

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Power and EnergyElectric Power is measured in WattsElectric Energy is measured in Watts-hr.1 watt-sec= JouleElectric power = voltage × current, or

P = V × I