FOR BHS PHYSICAL SCIENCE9 T H GRADE

Electronics Introduction

What is Electricity

What does Electricity mean to you?

Where does it come from, how does it work?

Electricity

It is the many physical quantities and properties associated with electrical charges.

This area of science is responsible for all electronics devices and an integral part to all modern science.

Types of Charges

Electricity is dependent at two main types of charges positive and negative.

Electrons are particles that have the negative charge and are free to move in atoms.

Electric Force

Opposite charges repel and like charges attract

This electric force increases based on distance and larger amounts of charge.

Electric Field

Electric field also depends on the distance and amount of charge like electric force.

Current (I)

Current is the flow of charged particles (usually electron)

Currents symbol is I and it’s units are in ampere’s often abbreviated as A.

Two main types of current exist AC and DC

AC vs. DC

DC means direct current and is when charge particles only flow in one direction.

AC means alternating current and is when current changes direction periodically. (This means it has wave like properties)

Resistance (R)

Resistance is the opposition to the flow of charges in a material (aka current).

Resistance is dependent on the material, it’s length, thickness and temperature.

Conductors

Conductors have a relative low resistance and thus readily conduct current.

Good thermal conductors are almost always good electrical conductors. So, copper, aluminum, etc. are good conductors.

Insulators

Insulators have a rather high resistance and thus gives current a hard time.

Thermal insulators are again often electrical insulators. So, wood, rubber and air are good insulators.

Voltage (Potential Difference)

A difference in energy between two locations that allows current to flow. (So, if Voltage equals 0 there can be no current)

Voltage (V) is measured in Volts and named after an Italian Physicist Volta who invented one of the first batteries.

Ohm’s Law (VIR)

Ohm’s law is the simple linear relationship between voltage to current and resistance. V = I R

This equation is a foundation to analyzing circuits. Such as for example, V= I R gives (9 V) = I (100 Ω) which yields I= 9 V/ (100 Ω) = 0.09 Amps for the circuit below.

Electric Power (PIV)

Electric Power is equal to current times voltage. So, P= I V

This means that for the previous circuit, with a voltage of 9 V and current of 0.09 A,

that power is P = (9 V) (0.09 A) yields P = 0.81 Watts

Static Electricity

Is the build up of electrical charge on an object.

This objects can build up charge by friction, contact and induction.

Contact Charging

By using friction you can exchange electrons with an object thus building a net charge.

By contact with a charged object, you can drain the charge to you.

Magic?

By bringing a charged object near a non-charged object, you can cause the non-charged object attract the charged object!

What is this magical phenomenon, you may ask?

Induction

We call this induction and it occurs by the free electrons of the non-charged object rearranging in such a way to produce an apparent charge. Although, the non-charged object is still neutral.

Circuit Diagrams

Circuit diagrams use symbols to represent parts of the circuit.

This is basically a blue print for how to build a devices electrical part.

Series Circuit

If one element in a series circuit stops functioning, all elements stop.

Not useless! If a circuit stops functioning during a power surge it can save the other elements.

Parallel Circuit

If one element in a circuit stops functioning, the rest can still operate.

This is how a homes fuse box is wired.

Grounding (Earth Ground)

Grounding is when a wire goes directly into the earth.

The earth is ideally a giant conductor and thus soaks up the current that goes to it.

Used as a safety for open circuits. If a device short circuits the earth is a better conductor than you are and thus the charge goes to it instead of you!

Fuse

A fuse is an electrical component that melts down and protects the rest of the circuit from power surges.

This can stop your home’s electrical components from exploding during a power outage.

Electronics Devices!

The science of using an electrical signal to transmit, process or store information is electronics!

Types of Signal

Two main types:

Analog signals which can vary both in amplitude and frequency. (Yes, waves are back to haunt you)

Digital which have two states for amplitude high and low or rather 0 and 1. Binary signals.

Semiconductors

A magical material that can be both an insulator or conductor under certain conditions.

This material allows for some of the most important electrical components to modern life.

Solid-State Components

Modern technologies heart! The vital foundation for computers, cell phones, iDevices, etc.

Three types we will cover:

Diodes, Transistors and Integrated Circuits

Diodes (d)

Only allow current to flow in one direction.

This allows you to convert AC to DC current.

Transistors (Q)

Can be used as electronic switches, amplifiers, a changing resistor and much much more.

These in particular, are responsible for all computers!

Integrated Circuits (IC)

These marvelous components are simply many components built on a silicon chip and thus are extremely small.

IC’s are often just many transistors combined.