Physics

Laboratory II

Ins. Fatma Nur AKI

fnaki@ticaret.edu.tr

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CONTACT INFORMATION (SEE ALSO IN LAB MANUAL/ON WEBSITE)

Ins. Fatma Nur AKI

fnaki@ticaret.edu.tr

444 04 413 (#3218)

See course website

http://ww3.ticaret.edu.tr/fnaki/

COURSE INFORMATION

Reports ( 20 %)

Attendance (5%)

Project (25%)

Final Exam ( 55 %)

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FUNDAMENTAL FORCES

Forces/interactions can be described as exchange

of mediating gauge bosons

Strong Interaction:

Gluon g m=0 Q=0 Spin=1

Weak Interaction: W+, Z0

m=80, 91GeV Spin=1

Electro-magnestism:

Photon g m=0 Q=0 Spin=1

Gravity:

Graviton G m=0 Q=0 Spin=2

SUB-ATOMIC DIMENSIONS

PARTICLE PHYSICS

Point like

Point-like

…small, smaller…extremely small!…

A small stone < 1 hair

> 30 soccer fields

FORCES IN NATURE

Force Intensity Carriers Happens in

Strong Nuclear ~ 1 Gluons

(massless)

Atomic nuclea

Elettro-magnetic ~ 10-3 Photons

(massless)

Atomic levels

Weak Nuclear ~10-5 W+,W-,Z0

(heavy)

Beta radioactive decay

Gravitation ~10-38 Gravitons (?) Heavy bodies

Interactions happen by exchange of one or more particles (carriers or bosons)

FORCES AND DISTANCES

R ~ 10-15

m (forza forte)

R ~ 10-10

m (forza elettromagnetica)

R > 106 m (gravitational force)

Tevatron LHC LHC Upgrade ILC

2006 2007 2012

SCIENCE TIMELINE

LARGE HADRON COLLIDER (LHC)

proton-proton collider at CERN (2007)

14 TeV energy

7 mph slower than the speed of light

cf. 2TeV @ Fermilab

( 307 mph slower than the speed of light)

Typical energy of quarks and gluons 1-2 TeV

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LHC IS BIG….

ATLAS is 100 meters underground, as deep as Big Ben is tall

The accelerator circumscribes 58 square kilometers, as large as the island of Manhattan

ELECTROSTATIC

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VIDEOS

https://www.youtube.com/watch?v=T0J5q43MSw

8 static electricity

https://www.youtube.com/watch?v=R-

rF1ygeGww

https://www.youtube.com/watch?v=6IeeshkVATY

https://www.youtube.com/watch?v=6IeeshkVATY

https://www.youtube.com/watch?v=3Ptu07enIsY

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FUNDAMENTAL QUANTITIES AND SI UNITS

Length meter m

Mass kilogram kg

Time second s

Electric Current ampere A

Thermodynamic

Temperature

kelvin K

Luminous Intensity candela cd

Amount of Substance mole mol

Why should we care about SI units?

SYSTEM OF UNITS

We will use the SI system – SI International System of Units

Fundamental Quantities Length meter [m]

Mass kilogram [kg]

Time second [s]

Other Units Current ampere [A]

Derived Quantities Force newton 1 N = 1 kg m / s2

Energy joule 1 J = 1 N m

Charge coulomb 1 C = 1 A s

Electric Potential volt 1 V = 1 J / C

Resistance ohm 1 = 1 V / A

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ATOMS…

Have neutrons, protons, and electrons.

Protons are positively charged

Electrons are negatively charged

ELECTRONS…

Are located on the outer edges of atoms…they can be moved.

A concentration of electrons in an atom creates a net negative charge.

If electrons are stripped away, the atom becomes positively charged.

+ -

+

+

+ +

THE WORLD IS FILLED WITH

ELECTRICAL CHARGES:

+

+

+

+

+

-

- - -

-

-

- - -

CHARGE IS QUANTIZED

q = multiple of an elementary charge

e:

e = 1.6 x 10-19 Coulombs

Charge Mass Diameter

electron - e 1 0

proton +e 1836 ~10-15m

neutron 0 1839 ~10-15m

positron +e 1 0

(Protons and neutrons are made up of quarks, whose charge is

quantized in multiples of e/3. Quarks can’t be isolated.)

COULOMB’S LAW

q1 q2

r12 r12

F12

Force on 2 due to 1 F12 kq1q2

r12

2ˆ r 12

k = (4pe0)-1 = 9.0 x 109 Nm2/C2

e0 = permitivity of free space

= 8.86 x 10-12 C2/Nm2

Coulomb’s law describes the interaction between bodies due to their charges

WHAT IS THIS ELECTRICAL

POTENTIAL CALLED?

Static Electricity

- - -

- -

-

- + + + +

+

STATIC ELECTRICITY

The build up of an electric charge on the surface of an object.

The charge builds up but does not flow.

Static electricity is potential energy. It does not move. It is stored.

STATIC DISCHARGE…

Occurs when there is a loss of static electricity

due to three possible things:

Friction - rubbing

Conduction – direct contact

Induction – through an electrical field (not

direct contact)

What’s the fundamental criterion for initiating a

lightning strike?

Ans. E > 3 MV/m

WHAT IS ELECTRIC / ELECTRıCıTY ?

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Electrical current ?

Electric Power ?

Electric Potential Energy ?

Electrical Charge ?

Electric Field ?

What is static electricity?

When two objects rub against each other electrons transfer and

build up on an object causing it to have a different charge from

its surroundings.

Like the shoes rubbing against the carpet. Electrons are

transferred from the carpet to the shoes.

The van de Graaf generator (large silver ball) deposits

electrons on the ball. When a person places their hand

on the ball and the machine is turned on, electrons are

transferred to and collected on the person touching the

silver ball.

Why do you

think this

machine affects

the hair of the

children in the

picture?

What causes you to be shocked when you rub your feet across

carpet?

An electrical discharge is the passing of an electric current

through the air from a negatively charged object to a positively

charge object. This is what causes lightning!

ELECTRICITY THAT MOVES…

Current: The flow of

electrons from one place to

another.

Measured in amperes (amps)

Kinetic energy

HOW CAN WE CONTROL CURRENTS?

With circuits.

Circuit: is a path for the flow

of electrons. We use wires.

What is the difference between static

electricity and current electricity?

Static electricity is stationary or collects on the surface of an

object, whereas current electricity is flowing very rapidly through

a conductor.

The flow of electricity in current electricity has electrical

pressure or voltage. Electric charges flow from an area of high

voltage to an area of low voltage.

Water pressure

and voltage

behave in similar

ways.

The pressure of the water flowing through the pipes on

the last slide compare to the voltage (electric potential)

flowing through the wires of the circuit. The unit used

to measure voltage is volts (V).

The flow of charges in a circuit is called current.

Current (I) is measured in Amperes (A).

How does electric current heat this light bulb filament?

Where does the energy come from?

Answer: Collisions between e & ions. e accelerated by E.

ELECTRIC CIRCUTS

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A Simple Electric Circuit

Current flow

batery

CURRENT IN ELECTRIC CIRCUITS

An electric Circuit is a

closed loop.

Basic Circuits consist of

three things:

Electron pump

(Battery)

Device that reduces

potential. (User)

Conducting

connections

(Wires)

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What are the three effects of electric current?

Death, injury, and electricution .

If we ignore the above, humourous(!), attempt at an answer, then

the three effects of an electric current are

(1) heating effect,

(2) chemical effect, and

(3) magnetic effect.

Examples of the heating effect include electric heaters, kettles,

stoves, etc. An examples of the chemical effect is electroplating.

Examples of the magnetic effect includes relays, motors, etc.

The SI unit of current, the ampere, is defined in terms of the

force between two parallel conductors due to their magnetic

fields (i.e. the magnetic effect).

ELECTRICAL

PRINCIPLES

Energy,

Voltage,

Voltage Types, AC/DC,

Current,

Power,

Resistance, Heat, and Light

ENERGY

Energy – Is the capacity to do work. There are two types of Energy – Potential and Kinetic.

Potential Energy – Stored Energy. Example: Battery.

Kinetic Energy – Energy in motion. Kinetic Energy is released Potential Energy. Example: Battery operated electric motor.

VOLTAGE

Voltage: Is the amount of electrical pressure in a circuit.

Voltage is measured in Volts (V).

Voltage is also known as ElectroMotive Force (EMF) or

Potential Difference.

Pressure

This parasailer landed on a

138,000-volt power line.

Why didn’t he get

electrocuted?

He touches only 1 line – there’s no potential

differences & hence no energy transfer involved.

VOLTAGE

Voltage is produced any time there is an excess of electrons at one terminal of a Voltage source and a deficiency of electrons at the other terminal.

Voltage may be produced by electromagnetism (generators), chemicals (batteries), light (photocells or solar cells), heat (thermocouples – Nuclear power), pressure (pizioelectricity – electronic drum pads), or friction (static electricity).

Homework !!

What is pizioelectricity?

CURRENT

Current (I) flows through a circuit when a source of

power is connected to a device that uses electricity.

Current (I) is the amount of electrons flowing through an

electrical circuit.

Current (I) is measured in Amperes (A).

Current

CURRENT

An Ampere is the number of electrons passing a given point in one second.

The more power a load requires, the larger the amount of Current flow.

Current may be direct (DC) or alternating (AC).

Two types of Current Flow – Conventional Current Flow and Electron Current Flow.

POWER Power (P) is the rate of doing work or using energy.

Power may be expressed as True Power (PT ) or Apparent Power (PA).

True Power (PT ) (Gerçek Güç) is the actual power used in an electrical circuit.

Apparent Power (PA) (Görünür Güç) is the product of the voltage and current in a circuit calculated without considering the phase shift that may be present between the voltage and the current in the circuit.

Electrical Calculations – What is Ohm’s Law?

I = 3 V

2 Ω I = 1.5 amps

What are electric circuits?

Circuits typically contain a voltage source, a wire conductor, and one or more devices which use the electrical energy.

What is a series circuit?

A series circuit is one which provides a single pathway for the current to flow. If the circuit breaks, all devices using the circuit will fail.

What is a parallel circuit?

A parallel circuit has multiple pathways for the current to flow. If

the circuit is broken the current may pass through other

pathways and other devices will continue to work.

How is Electrical Power calculated?

Electrical Power is the product of the current (I) and the voltage

(v)

The unit for electrical power is the same as that for mechanical

power in the previous module – the watt (W)

Example Problem: How much power is used in a circuit which is

110 volts and has a current of 1.36 amps?

P = I V

Power = (1.36 amps) (110 V) = 150 W

How is electrical energy determined?

Electrical energy is a measure of the amount of power used and

the time of use.

Electrical energy is the product of the power and the time.

Example problem:

E = P X time

P = I V

P = (2A) (120 V) = 240 W

E = (240 W) (4 h) = 960Wh = 0.96 kWh

COMPONENTS OF ELECTRICAL

SYSTEM

Voltage source = generator/batteries

Conductor = wires

Control Element = switch

Load = light bulb, motors, appliances

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ELECTRıC CIRCUITS

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CIRCUITS, SYMBOLS, & ELECTROMOTIVE FORCE

Common circuit symbols

All wires ~ perfect conductors V = const on wire

Electromotive force (emf) = device that maintains fixed V across its terminals.

E.g., batteries (chemical),

generators (mechanical),

photovoltaic cells (light),

cell membranes (ions).

BATTERY CONSTRUCTION

In its simplest form a battery

consists of two different metal

(copper&zinc) plates called

electrodes which are dipped

into an acid solution called

electrolytes

The cell then produces

current through the path of

the two metals

BATTERY TYPES

Primary cells Nonrechargeable

Alkaline

Carbon-Zinc

Lithium

Mercury

Silver-Oxide

Secondary

cells Rechargeable

Lead-Acid

Nickel-Iron

Nickel-Cadmium

Lead-Calcium

Silver-Zinc

GÜÇ KAYNAĞı

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1Joule / Coulumb = 1Volt.

ε=dW/dQ P=dW/dt =ε.I

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(RESISTOR

The electrical resistance of an electrical

conductor is the opposition to the passage of an

electric current through that conductor; the

inverse quantity is electrical conductance,

the ease at which an electric current passes.

Electrical resistance shares some conceptual

parallels with the mechanical notion of friction.

The SI unit of electrical resistance is the ohm

(Ω), while electrical conductance is measured

in siemens (S).

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POTENTIOMETER

A variable resistance.

Used for dimmers, fan speed

controls, etc.

SEMICONDUCTORS

Semiconductors are a third class of materials,

and their electrical properties are somewhere

between those of insulators and those of

conductors.

Silicon and germanium are well-known examples

of semiconductors commonly used in the

fabrication of a variety of electronic devices, such

as transistors and light-emitting diodes.

The electrical properties of semiconductors can be

changed over many orders of magnitude by the

addition of controlled amounts of certain atoms to

the materials.

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SUPERCONDUCTIVITY

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Superconductivity is a phenomenon of exactly zero

electrical resistance and expulsion of magnetic fields

occurring in certain materials when cooled below a

characteristic critical temperature.

It was discovered by Dutch physicist Heike

Kamerlingh Onnes on April 8, 1911 in Leiden. Like

ferromagnetism and atomic spectral lines,

superconductivity is a quantum mechanical

phenomenon.

It is characterized by the Meissner effect, the

complete ejection of magnetic field lines from the

interior of the superconductor as it transitions into

the superconducting state. The occurrence of the

Meissner effect indicates that superconductivity

cannot be understood simply as the idealization of

perfect conductivity in classical physics.

CAPACITORS

CAPACITORS (C)

A capacitor (originally known as a condenser) is a

passive two-terminal electrical component used to store energy electrostatically in an electric field.

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SERIES CIRCUITS

Only one path for current to follow

User followed by another user (ie. Resistor

followed by a light)

...321

VVVVequ

…

Festive lights decorate a city.

If one of them burns out, they all go out.

Are they connected in series or in parallel?

SERIES CIRCUIT RULES

Current is the same for each user

The effective resistance is the sum of all

resistors in the series

The sum of the voltage drop is equal to the

total voltage drop

...321

RRRRequ

...321

VVVVequ

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Ampermeter & Voltmeter

ELECTRICAL MEASUREMENTS

A voltmeter measures potential difference between its two terminals.

Ideal voltmeter: no current drawn from circuit Rm =

CONCEPTUAL EXAMPLE

MEASURING VOLTAGE

What should be the electrical resistance of an ideal voltmeter?

An ideal voltmeter should not change the voltage

across R2 after it is attached to the circuit.

The voltmeter is in parallel with R2.

In order to leave the combined resistance, and

hence the voltage across R2 unchanged, RV must

be .

AMPERMETERS

An ampermeter measures the current flowing through

itself.

Ideal voltmeter: no voltage drop across it Rm = 0

OHMMETERS & MULTIMETERS

An ohmmeter measures the resistance of a component.

( Done by an ammeter in series with a known voltage. )

Multimeter: combined volt-, amp-, ohm- meter.

PARALLEL CIRCUITS

Two or more paths for current to follow

PARALLEL CIRCUIT RULES

Total current in the circuit is the sum of the current in all its paths (branches)

The equivalent resistance decreases with more parallel resistors

Voltage is the same in each path.

...321 IIIItot

...1111

321

RRRR

equ

25.3. KIRCHHOFF’S LAWS & MULTILOOP

CIRCUITS

Kirchhoff’s loop law:

V = 0 around any closed loop.

( energy is conserved )

This circuit can’t be analyzed using

series and parallel combinations.

Kirchhoff’s node law:

I = 0 at any node.

( charge is conserved )

INDUCTORS

INDUCED EMF PRODUCED BY A

CHANGING MAGNETIC FLUX!

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dt

de

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