Static and Current Electricity

Ms Rochford

Third Year Science

In this topic:

• Static electricity • What is charge? • Static electricity as a force • Earthing • Lightning • Insulators and Conductors • Electrical circuits • Ohm’s Law

Let’s make some static!

Static Electricity

• What causes static electricity?

Click on the dog picture to watch the YouTube clip

The Atom

• Nucleus = centre of the atom

• Neutrons = neutral (no charge)

• Protons = positive charge

• Electrons = negative charge

The Atom

• Normal atoms: Number of

protons Number of electrons

Neutral charge

The Atom

• Too many protons: Number of protons

Number of electrons

Positive charge

The Atom

• Too many electrons: Number of protons

Number of electrons

Negative charge

Electrons and Electricity

• The Electron is responsible for almost all of electricity

There are two types of charges

• POSITIVE(+)

• NEGATIVE(-)

+-+-+-+-

Am I charged? +4 -4 = 0

Uncharged

There are two types of charges

Am I charged? +4 - 3 = +1

Positive charge

-++-+-+

Losing an electron causes a positive charge

There are two types of charges

Am I charged? +4 - 5 = -1

Negative charge

Gaining an electron causes a negative charge

+-+--+-+-

Is Static Electricity a force?

E Force: causes a stationary object to move

YES!

Static Electricity is a Force

Is Static Electricity a force?

E Force: causes a stationary object to move

Demonstrating force between charged objects

Opposite charges attract

each other

Like charges repel each other

So what is static electricity?

• As soon as it can, the object will discharge to go back to neutral or uncharged

• This can produce a ‘spark’ or a ‘shock’

Static electricity: an imbalance of positive and negative charges

Earthing

Earthing

• Earthing removes charge from a charged object

Earthing: when excess electrons are allowed to flow into the earth

Earthing

• This is designed for safety

Earthing: when excess electrons are allowed to flow into the earth

Lightning damage

• Lightning can damage buildings

• The electricity travels through the walls to the earth

Lightning Rods

• Made of good conducting metals (e.g. copper)

• Lightning goes through the conductor to earth

• The building is safe

Insulators and Conductors

Plastic Biro Paper pieces

ATTRACTS

Metal Pen Paper pieces

NO EFFECT

Insulators and Conductors

• The plastic biro was charged by rubbing it

• It stayed charged because it is an insulator

• The charge couldn’t flow out of the plastic

Insulator: a material through which charge cannot flow

Insulators and Conductors

• The metal pen was charged by rubbing

• The charge immediately flowed out of it

• No charge left to attract the paper

Conductor: a material through which charge can freely flow

CURRENT ELECTRICITY

What is an electrical circuit?

What is an electrical circuit?

• It’s a way of getting electrons to do a job safely

What is an electrical circuit?

• Electrons are stored in batteries and can move in wires

• When electrons pass through wires they heat up.

• This causes light to be radiated by the bulbs

What is an electrical circuit?

• Electrons always move from high to low potential

As electrons pass through the bulb wires they lose some potential

energy and eventually the

battery run out!

Rules for a Circuit

1. Electron source (a battery)

Rules for a Circuit

1. Electron source (a battery)

2. Path for them to move through i.e. A wire (conductor)

Rules for a Circuit

1. Electron source (a battery)

2. Path for them to move through i.e. A wire (conductor)

3. Continuity, the path must be continuous

Insulators and Conductors

• Can you remember?

Insulator: a material through which charge cannot flow

Conductor: a material through which charge can flow

Which one will light the bulb?

Any predictions?

SYMBOL for battery…

+ terminal - terminal

Symbols Used in Electricity

OP49

To distinguish between electrical insulators and conductors

Types of circuit

This is when the parts of the circuit are

connected like this...

‘Hand in hand’

Series Circuit

Types of circuit

If one bulb blows, the other won’t get any

electrons

Remember: electrons can’t jump through

empty space

Series Circuit

Types of circuit

This is when the components of the

circuit are connected like this...

‘one on top of each other’

Parallel Circuit

Types of circuit

If one blows the other will still get electrons!!

Parallel Circuit

Current

What is current?

Current

• A BATTERY acts like a PUMP

– it pushes the current round the circuit through devices like bulbs or speakers

Electric Current: a flow of electric charges being ‘pushed’ around a circuit

Current

Electric Current: a flow of electric charges being ‘pushed’ around a circuit

• Too many electrons per second can be Bad!!!

Unit of current

AMPERES or Amps (A)

Voltage

• It is the force that ‘pushes’ current through a circuit

• A flat battery will read 0 volts

Voltage: the potential a battery has to do work

Resistance

Resistance: a measure of how good a material is at stopping electrons

Unit of resistance

OHMS (Ω)

Resistors

Good Resistors

• Insulators are good resistors • They have high resistance value

Bad Resistors

• Conductors are bad resistors • They have low resistance value

Is there a relationship between the speed of water in a pipe and the

power of the water pump?

Is there a relationship between the current of electrons in a circuit and the

voltage of the battery?

Ohm’s Law

Ohm’s Law: voltage is directly proportional to current

V

I R

Ohm’s Law

• Another way to state Ohm’s law is:

Potential (volts) equals current (amps) times the load (ohms).

• In a basic circuit, one of the three values can be calculated from the other two.

Ohm’s Law

V = voltage (Volts)

I = current (Amps)

R = resistance (Ohms)

V = I×R

The most important electronics equation:

V

I R

OP50

Ohm’s Law: To measure current, voltage and resistance and to establish a

relationship between them

Ohm’s Law Circuit Diagram

Drawing our Graph

Current (Amps)

Vo

ltag

e (

Vo

lts)

(0, 0)

This is a directly proportional relationship

Definition How is it formed?

Static Electricity

Force between charged objects

Insulator Conductor Lightning &

lightning rods

Earthing

Current: • Definition • Units

Voltage: • Definition • Units

Current Electricity

Resistance: • Definition • Units • Examples of

resistors

Conductors & insulators in a circuit

Rules for a circuit

Ohm’s Law: • Definition • Equation • Graph

Types of circuit

Chapter 42: STATIC & CURRENT ELECTRICITY

DONE!!