Introduction

1

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)

4

Components of Electric circuit

5

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)

6

Activity1) Collect your

activity packet2) Learn how to use

multimeter.• All measuments

only DC in this class

• Only milli Ampere of current measured

7

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?

8

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?

9

Series

▫Connect resistors in series.

ParallelVoltages in parallel

Resistors in parallel

10

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

11

12

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

13

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