Equipment unit 3: electric circuits

Basic Laws of Magnetism:

#1 Diploes (2 poles) #2 Attraction and Repulsion #3 Inverse square law

1 Watt=

1 A of current flowing through 1 V of electrical power

What conditions are needed for current flow?

1) conductors 2) potential difference 3) Resistance

Retentivity:

Ability of a material to stay magnetized

Magnetic classifications of matter:

All MATTER is classified according to the manner in which it interacts with an external magnetic field. The degree of magnetism of a substance is related to the number of unpaired electrons in the outer shell

Series circuit

All circuit elements are connected in one following another in a ring

The alloys of ferromagnets

Alnico, permalloy

Non magnetic =

Diamagnets

What can exhibit a weak form of magnetism only in the presence of an external magnetic field?

Diamagnets

un-magnetized object=

Domains point in different directions and cancel one another out

Permeability:

Ease with which a material can be magnetized

Diploes (2 poles)

Every magnet has both a North pole and South pole

What makes strong magnets?

Ferromagnents

Curls in the direction of the magnetic field lines surrounding the conductor

Fingers

How does current flow along a conductor?

Flemings right hand rule

Inverse square law:

Force between 2 magnetic fields is directly proportional to the product of their magnitudes and inversley proportional to the square of the distance between them.

Attraction and Repulsion

Like poles repel; unlike poles attract

At the center of the coil:

Magnetic field is concentrated and strong (field outside is divergent and weak)

Artificially induced permanent magnets:

Magnets produced from magnetic material

Diamagnets:

Materials that are unaffected and are repelled by magnetic fields - tend to weaken the magnetic field in the vicinity

A charge AT REST produces ____ current

NO

V=IR

Ohm's Law

Power Law=

P=IV

The instantaneous electrical power P delivered to a component is the product of voltage and current, which may be expressed in mathematical terms as

P=IV

this law applies to IN-coming electrical power

P=IV

P=IV:

Power (watts) = Current (amps) x Voltage (volts)

What is the opposite from a conductor?

Resistor

The ______________ refers to a loop of wire (conductor), wrapped around a metallic core, which produces a magnetic field when an electrical current is passed through it.

Solenoid

Inside the conductor/core magnetic lines travel:

South to north

Magnetic lines of force always flow from ______________ to _____________ INSIDE the magnet

South to north

Points to the direction of the current (electron) flow

Thumb

Ex of Diamagnets

Water, wood, rubber, glass, plastic Some metals: mercury, lead, gold, bismuth

What is electric power measured in?

Watts

Whenever an electric current flows through a conductor, what surrounds the conductor?

a magnetic field

When an electric current is conducted through a wire what happens?

a magnetic field is created

Magnetism:

ability of a material to attract certain objects

in parallel circuit To get total resistance of all components

add the reciprocals of the resistances of each component and take the reciprocal of the sum

in a parallel circuit the amperage (current) is

additive

in a series circuit, voltage and resistance is

additive

Electric power

amount of work done by an electric current

How can magnetic fields be concentrated?

by coiling the conductor

in a parallel circuit the voltage is

constant

in a series circuit, amperage is

constant, meaning that current through each circuit element is the same

Parallel circuit

contains elements that bridge conductors rather than lie in a line along a conductor

magnetic field in motion=

current

I=

current (measured in amperes)

Ohm's law defines the relationship between what?

current, voltage, and resistance

Under Ohm's Law increasing resistance=

decreases the current flow if the voltage is not changed

Magnetized object=

domains are pulled about until they point in the same direction, thus reinforcing eachother

Rate at which electrical energy is transferred, used, or stored=

electric power

it is the energy produce or consumed per unit time

electric power

conductors

electrical connectors that readily conduct electric current through electrical conduction

What are temporary magnets produced by using a wire wrapped around an iron core?

electromagnets

Voltage AKA

electromotive force (EMF)

What are artificially induced permanent magnets manufactured from?

from steel alloy: alnico

A resistor with a low value of resistance is a ___________ conductor

good

Domain theory of magnetism:

group of atoms with their diploes aligned and magnetic field moving in the same direction

Under Ohm's Law increasing voltage=

increases current, provided resistance does not change

As an object gets further away, the influencing field decreases because of the increased area it affects describes what?

inverse square law

Ex of Ferromagnets:

iron, steel, cobalt, nickel

voltage

is the push behind the current to make it move.

What causes voltage?

it is caused by potential difference and is the quantitative expression of potential difference.

Ex of paramagnets

liquid oxygen, contrast agents used in MRI

Naturally occurring magnets

lodestone magnetite, a magnet mineral from iron dioxide earths magnetic field, bc it spins on an axis

Magnetic domain is AKA

magnetic diploes

A charge IN MOTION induces a

magnetic field

Imaginary lines of force are called?

magnetic lines of induction

Magnetic domain is the accumulation of?

many atomic magnets with their diploes aligned

Magnet:

material or object that produces a magnetic field

Ferromagnets

materials that when placed in an external magnetic field, become magnetized and remain magnetized even after the material is no longer in the field - High permeability

potential difference

measure of the amount of energy required to move a charged particle from point A to point B, through a resistor

Ohm's Law:

most important basic law of electricity in circuity

magnetic field at a constant=

no current

Magnetic lines of force always flow from ______________ to ____________ OUTSIDE the magnet

north to south

Outside the conductor/core magnetic field lines travel:

north to south

What is resistance measured in?

ohms

Resistance

opposes or hinders amount of current that is flowing through

A resistor with a high value of resistance is a ______________ conductor

poor

V=

potential difference (measured in volts)

Magnetic induction

process where an object or material is magnetized by an external magnetic field

Electric power in a circuit:

rate at which energy is absorbed within a circuit

"opposition to a force"

resistance

What determines the amount of current through an object for a given voltage across that object?

resistance

Who's reciprocal quantity is electrical conductance?

resistance

R=

resistance (measured in Ohms)

What are conductors that slow down the passage of electric charge?

resistor

When grasping a conductor with the right hand, the direction of the magnetic field lines can be determined by using the what?

right- hand rule

Paramagnets:

slightly attracted to a magnet and loosely influenced by an external magnetic field (somewhat magnet)

The bigger the resistance, the ______________ the current going through

smaller

The more domains that are aligned, the ____________ the magnetic field in the material

stronger

Magnetic field disappears when current ceases, making these electrical magnets __________

temporary

What happens if that bar is removed from the field after a short time?

the dipoles will return to their random orientation, thus leaving the bar in-magnetized

When a non- magnetized iron bar is brought within the lines of force of a strong magnet what will the dipoles do?

the dipoles will temporarily align themselves with the lines of force passing through the iron bar.

intensity of the magnetic field is proportional to what?

the electric current

The greater the voltage, the greater ...

the flow of electrical current

where is magnet effect strongest at?

the poles

Why is a conductive pathway needed?

to allow the electrons to flow

electric circuit

unbroken path along which an electric current exits or flows

Resistor

used to limit or regulate the flow of electrical current in a circuit, inhibits flow of electrons

volt=

watt