The Atom

NucleusNucleus

ElectronElectron(negative)(negative)

ProtonProton(positive)(positive)

NeutronNeutron(no charge)(no charge)

P4

Charging by FrictionCharging by FrictionDuster rubbed over surface of Glass - Friction causes outer electrons of atoms near the edge to be removed.

Glass Rod - showing atoms

(enlarged) with only outer

electron showing.

Electron Negative Charge

NucleusPositive Charge

Some outer electrons rubbed onto the duster - leaving atoms behind with a net positive charge

Duster Duster ends up ends up

with with negativenegative

chargecharge

Rod ends up Rod ends up with with positivepositive

chargecharge

Charging by Friction

Rubbing the Glass rod strips some of the __________ from Rubbing the Glass rod strips some of the __________ from some of the atoms at the edge of the rod. some of the atoms at the edge of the rod.

This leaves these atoms with a net ________ charge. This This leaves these atoms with a net ________ charge. This means that overall the Glass rod has a __________ charge as means that overall the Glass rod has a __________ charge as the other atoms have equal numbers of positive and the other atoms have equal numbers of positive and __________ charges (called neutral). Perspex and Acetate __________ charges (called neutral). Perspex and Acetate also behave like this. also behave like this.

In other materials such as Polythene the electrons are In other materials such as Polythene the electrons are rubbed off the cloth onto the insulator, giving the material rubbed off the cloth onto the insulator, giving the material a net __________ charge.a net __________ charge.

Electrostatic Law :-Electrostatic Law :-““Like charges _______Like charges _______ ;;______ charges ________”.______ charges ________”.

Charging by Friction

Rubbing the Glass rod strips some of the __________ from Rubbing the Glass rod strips some of the __________ from some of the atoms at the edge of the rod. some of the atoms at the edge of the rod.

This leaves these atoms with a net ________ charge. This This leaves these atoms with a net ________ charge. This means that overall the Glass rod has a __________ charge as means that overall the Glass rod has a __________ charge as the other atoms have equal numbers of positive and the other atoms have equal numbers of positive and __________ charges (called neutral). Perspex and Acetate __________ charges (called neutral). Perspex and Acetate also behave like this. also behave like this.

In other materials such as Polythene the electrons are In other materials such as Polythene the electrons are rubbed off the cloth onto the insulator, giving the material rubbed off the cloth onto the insulator, giving the material a net __________ charge.a net __________ charge.

Electrostatic Law :-Electrostatic Law :-““Like charges _______Like charges _______ ;;______ charges ________”.______ charges ________”.

electronelectronss

positivpositiveepositivepositive

negativenegative

negativenegative

repelrepelUnlikUnlikee

attracattractt

Static Electricity : Charging Problem

Planes become charged as dusty air rubs against them in flight

They are earthed by connection to the ground when refuelling.

This stops sparks jumping near the fuel nozzle.

Static Electricity : Useful Charging

The paint is charged as it comes out of the nozzle.

The paint is attracted to the car.

The car must be earthed or connected to a positive voltage.

Another use of static: Electrostatic Precipitators.

Precipitator

1. Dust particles collect negative charges as they flow past

2. Positive plates attract the negative charged particles

3. Plates are tapped and the charged particles fall into the hoppers

liveliveearthearth

neutralneutral

fusefuse

cord gripcord grip

Fuse

• Thin Tin wire in a glass or ceramic case (with metal ends)

• Wire chosen so that it melts (‘blows’) if too much current flows

• Disconnects live pin from the wire/appliance when it melts

• Can be chosen from 3A, 5A, 10A, 13A• Choose fuse with next highest current

value e.g. TV uses 4A – choose 5A fuse

Circuit breakers and RCD’s

• Circuit breakers work like fuses• Disconnect the live (‘trip’) when current is

too high• Can be reset (no need to change fuse!)• Work by using electromagnetic or thermal

switches• Residual Current Devices (RCD’s) are

more sensitive and disconnect the live if any current is measured in the Earth wire- useful for lawn mowers etc.

• If you double the voltage, but the resistance stays the same, you double the current.

• If you double the resistance, but the voltage stays the same, you halve the current.

V = I x RVoltage = Current x Resistance

I =

R =

1) Pre-natal scanning

2) Cleaning – it can be used to dislodge dirt

3) Detecting flaws or cracks

4) Medical treatment e.g scans

What is it used for ?

Ultrasound is sound of such a high frequency that we cannot hear it (i.e above 20 000 Hz)

How does it work?

The waves are reflected off the different layers

Is this a stable (balanced) atom?

Why?

What is the MASS NUMBER?5 (three Protons & two Neutrons)

MASS NUMBER = number of protons + number of

neutrons

SYMBOL

ATOMIC NUMBER = number of protons

What do you notice?

So, what is an alpha particle?

What do you notice?

The Atomic number decreases by a value of 1.

What do you notice?

The atomic structure doesn’t fundamentally change.

Half Life

Gamma source

The gamma radiation from the radioactive source is picked up above the ground, so the leak in the pipe can be detected.

Gamma - tracers

Radiotherapy

X-Rays and Gamma Rays

Gamma rays come from the nucleus of an atom, x-rays come from a machine which fires electrons at metal targets.

Therefore x-rays are easier to control than gamma rays.

They both give out similar wavelengths

(Both are electromagnetic

waves)

Nuclear Fission

This energy is used to heat water into steam.

The steam drives round a turbine.

The turbine drives a generator (dynamo).

The Earth and the MoonThe Earth and the MoonThe Earth’s gravity attracts the Moon, in the same way the Moon’s gravity attracts the Earth.

It is the gravitational attraction of the Moon which causes the tides in the oceans on Earth.

gravitational force

Provides centripetal forceFaster

Heavier

Smaller circle/ ellipse

BIGGER Centripetal force

P5

Resultant ForceResultant Force

When two forces act at different angles on a body, the resultant force is calculated using the parallelogram of forces...

Force from tug 1

Forc

e fro

m tu

g 2

Resultant force

Constant Acceleration Formulas - SummaryConstant Acceleration Formulas - Summary

Symbol Meaning Unit

v final velocity m/s

u initial velocity m/s

s distance travelled m

t time taken s

a acceleration m/s2

We have 4 formulas. These formulas will help you calculate any motion problem in which a body undergoes zero or constant acceleration.

Formulas

s = (u + v ) x t 2

s = ut + ½at2

v = u + at

v2 = u2 + 2as

Whenever you have any 3 of the five ‘v-u-s-t-a’ unknowns, you can find out the remaining 2 unknown values by using one or more of the above formulas…

A tourist drops a croissant from the top of the Eiffel Tower.The croissant falls for 8 seconds.Ignoring air resistance, how high is the Eiffel Tower?

ExampleExample

Use...

s = ut + ½ at2

s = 0 x 8 + ½ x 10 x 82

The Eiffel Tower is 320m tall

s = 320m

v =

u =

s =

t =

a =

0

8

10

Horizontal

Vertical

Ignoring air resistance, the only force acting on a projectile during the flight is gravity.

Projectiles have a downward acceleration (due to gravity) and this only affects the vertical velocity.

For a projectile there is no acceleration in the horizontal direction.

Projectile Motion - Forces ActingProjectile Motion - Forces Acting

Calculating Time TakenCalculating Time TakenExample: Calculate the time taken, from firing, for the cannon ball to hit the target.

t = d/s

t = 48/24

Time taken is 2s

t = 2

t = d/s is a formula that can be applied to solve problems, whenever velocity is constant...

Velocity is constant in the horizontal vector...

Calculate the final vertical velocity of the cannon ball as it hits the target. In this case a = g = 9.8ms-2 (9.8m/s2)

Calculating Final VelocityCalculating Final Velocity

Example:

v = u + at

v = 0 + 9.8 x 2

v = 19.6m/s

v = u + at is a formula that can be applied to solve problems, whenever acceleration is constant...

Final vertical velocity is 19.6m/s

v = 0 + 19.6

Conservation of MomentumConservation of Momentum

Impulse & Momentum - SummaryImpulse & Momentum - Summary

An impulse is a sudden force applied for a short

period of time.

An impulse causes(and is equal to) the

change in momentum.

= Force x Time= Change in Momentum

Impulse

The units ofimpulse are Ns

Geostationary - Equatorial Orbiting SatellitesGeostationary - Equatorial Orbiting Satellites

Geostationary satellites are used for telecommunication purposes, and they are also known as geosynchronous satellites.

Geostationary satellites are used for telephone signals and satellite TV broadcasts.

Three satellites can cover the whole surface of the Earth.

Pacific Ocean

AtlanticOcean

IndianOcean

Microwaves - Satellite CommunicationsMicrowaves - Satellite CommunicationsMicrowaves - Satellite CommunicationsMicrowaves - Satellite Communications

Microwaves pass through the Earth’s atmosphere with less interference than longer wavelengths (radio waves), so they are used to carry signals to satellites orbiting the Earth.

PolarisationPolarisation

light beam

beam of polarised light

polarising filter

Polarising filters polarise light because they are composed of long-chain molecules, which are aligned within the filter in the same direction, (e.g. vertically).

As unpolarised light strikes the polarising filter, the portion of the waves vibrating in any plane other than vertical,(e.g. horizontal waves) are absorbed by the filter.

Electromagnetic waves obey the wave formula:

Wave Equation

Wave Equation

Write the 3 formulas...

Frequency (f) x Wavelength ()=Wave Speed (v)(metre/second, m/s) (Hertz, Hz) (metre, m)

(v) (f) ()

Interference can be demonstrated using two speakers (1 metre apart), producing the same frequency sounds.

1 metre

Constructive interference Destructive interference

Peak

Constructive and Destructive Interference Constructive and Destructive Interference

Trough

The sound waves produced from these speakers cause interference.

Glass

Air

Snell's law also states that the refractive index of a medium can be calculated from the angles of incidence and refraction:

Refraction at a BoundaryRefraction at a Boundary

n = sin i sin r

n = sin 57º sin 33º

n = 0.838 0.544

The refractive index of the glass block is 1.54

Total Internal ReflectionTotal Internal Reflection

42º is known as the critical angle. Above this angle the light ray is reflected internally. This is known as total internal reflection and it is the phenomenon exploited by fibre optic cable technology.

Use the angle slider to see what happens when the angle at which the light enters a glass block is increased...

Convex Lenses - Light Ray DiagramsConvex Lenses - Light Ray DiagramsThe principal focus of a biconvex lens...

Convex Lenses - Light Ray DiagramsConvex Lenses - Light Ray Diagrams

Georg Simon Ohm 1789-1854

ResistanceResistance is anything that will

RESIST a current. It is measured in Ohms, a unit

named after me.

The resistance of a component can be calculated using Ohm’s Law:

Resistance = Voltage (in V)

(in ) Current (in A)

V

RI

P6

Current-voltage graphs

I

V I

V1. Resistor

2. Bulb

Explain the shape of each graph

A potential divider

R1

R2

V2 = R1 + R2

R2V0

V0

Motor Effect – left hand rule

AC Generator

Induced current can be increased in 4 ways:

1) Increasing the speed of movement

2) Increasing the magnetic field strength

3) Increasing the number of turns on the coil

4) Increasing the area of the coil

1) Alternating current into the primary coil

2) Current, passing through a coil, generates a magnetic field

3) Because the current is alternating, it generates a changing magnetic field

4) A changing magnetic field induces a current in the secondary coil

Power

• Reminder P = IV

• In a perfectly efficient transformer, the power in is equal to the power out.

• Or,

• So, if the Voltage doubles, the Current will halve.

Full-wave rectifiedHow does it work?

+6V-6V

A B OUTPUT

0 0 0

0 1 0

1 0 0

1 1 1

A B OUTPUT

0 0 0

0 1 1

1 0 1

1 1 1

OUTPUTAB

INPUTSOUTA B

0

1

0

1

0

1

0

1

0

1

0

0

AND GATE OR GATE

AB OUTPUT

INPUTSOUTA B

0

1

0

1

0

1

0

1

0

1

1

1

A OUTPUTINPUT

A OUT

0

1

1

0

A NOT gate swaps 0’s to 1’s and 1’s to 0’s.If it is placed after AND or OR gates, its turns them into NAND (NOT AND) and NOR (NOT OR) gates. It is sometimes called an inverter.

NAND GATE NOR GATE

INPUTSAB

OUTPUT

AB

OUTPUT

OUTA B

0

1

0

1

0

1

0

1

1

0

1

1

NAND

Figure 4.4.

INPUTSAB OUTPUT

AB

OUTPUT

OUTA B

0

1

0

1

0

1

0

1

0

1

0

0

NOR

Figure 4.5.

The basis of a latch is this pattern of linked NOR gates. They can also be made with NAND gates in a similar pattern.NOR gates work with negative pulses, NAND gates work with positive pulses.

A brief high (1) signal at one input results in a permanent high (1) signal at the latch output.

A brief high (1) signal at the other input causes a low (0) signal at the latch output.

A low (0) signal at both inputs leaves the latch output signal unchanged.