1 Introduction Current Electricity Moving chargeselectrons Current electricity

1 Introduction

Current Electricity Moving 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 Parameter Definition Units Symbol Measuring meter Current Flow of electrons Ampere (A) I Ammeter Voltage Potential difference Volts (V) V Voltmeter Resistance Opposing force to current Ohms (Ω) R Ohmmeter Power Energy used in 1 sec Watts (W) Joule/sec P Wattmeter Energy Joules Watt-hour

4 Circuits Objectives: 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)

Components of Electric circuit Circuit component Definition Examples Electric 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 5 Measure current, voltage and power Ammeter, Voltmeter, wattmeter

6 Symbols(review) the Ammeter Voltmeter resistor Switch battery Light bulb ▫ Light bulb

7 Activity 1) Collect your activity packet 2) Learn how to use multimeter. All measuments only DC in this class Only milli Ampere of current measured

8 Multimeter How to connect probes ▫ Connect red probe into “VΩm. A” slot ▫ Connect the black probe into “COM” How to set the dial to measure the right quantity ▫ To measure voltage, ▫ current and ▫ resistance What scale to choose? Resistance Voltage

9 Activity 1: Voltage 1) Measure voltage of batteries a) AA b)AAA c)D d)9 V 2) 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?

10 Series ▫ Connect resistors in series. Parallel Voltages in parallel Resistors in parallel

11 Voltage and Current Measure current for 1. 5 V, 100 ohms. Measure current for 1. 5 V, 1000 ohms. Voltage(V) Resistance( R) 1. 5 V 100 ohms 1. 5 V 1000 ohms Current (I) Relation between V and I

12 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 resistance emf is electromotive force Assumptions: Only for conductors, resistors called “ohmic materials” Materials that do not obey Ohm’s law are called “nonohmic” materials

13 Power and Energy Electric Power is measured in Watts Electric Energy is measured in Watts-hr. 1 watt-sec= Joule Electric power = voltage × current, or P=V×I