WK 9 ELECTROMAGNETISM

who invented the first battery?

volta

who discovered that electric current PRODUCES a magnetic field?

Dr. Oersted

what is electromagnetic induction?

production of an electric current

what is the 1st law of electromagnetism?

Faraday Law

current is induced by a MOVING magnetic field

how do you control magnitude of induced current?

1-strength of magnets

2-speed of motion

3-direction of motion

=90° most

=45° less

=0° least

4-shape of conductor

the more coils the more current induced

what is the right thumb rule?

current going up, magnetic field goes around.

it indicates magnetic field in a current carrying a wire.

what is a Helix- ?

coil of a wire alone

what is a helix with a current?

solenoid

what is a solenoid with an iron core?

electromagnet

what is the 2nd law of electromagnetism?

LENZ LAW

-the induced current flows in the opposite direction of the applied current.

-back EMF or principle of self induction

what is self induction?

the induction of an opposing EMF in a single coil by its own changing magnetic field

what is mutual induction?

magnetic field induces a current in a nearby helix.

-can only do this through an alternating current

-this is induction of a current from a second wire

what is a generator?

converts mechanical energy to electrical energy

how does a generator work?

1-wire coil between magnetic poles

2-coil is mechanically turned within field(armature), coil cuts through field as it moves & current is induced

what is a motor?

converts electrical energy to mechanical energy

how does a motor work?

induction passes through the coil, magnetic field of the induction interacts with permanent magnetic field causing coil to move.

what is the first type of motor?

1-SYNCHRONOUS (w/ sine wave)

=coil rotates at same frequency as current(I) (60Hz)

=used in timing circuits in older machines

what is the second type of motor?

2-INDUCTION

=stator and rotor

=uses electromagnets to create magnetic field to interact with current's(I) magnetic field

=★Type used to rotate anode in an xray tube

what is a transformer?

step up step down

=used to change the magnitude of current & voltage

transformers operate on the principle of what?

transformers operate on the principle of MUTUAL INDUCTION

where is the step up found in a transformer?

found in a tube circuit (AKA high voltage transformer-HVT)

where is the step down found in a transformer?

found in filament circuit (used to heat up cathode to boil off electrons)

what type of induction does a transformer need to have to work?

mutual induction

what is the transformer law voltage?

Vp Np

--- = ---

Vs Ns

what is the transformer law amperage?

Is Np

--- = ---

Ip Ns

what is an autotransformer?

a variable transformer that operates on self induction

what does the high voltage transformer do ?

when submerged in oil it reduces shock

what happens in an air core transformer?

2 solenoids

the magnetic field is all over and inefficient because it all escapes

what is an open core trasnformer?

a electromagnet, an iron core added to the air core(solenoids) to increase the strength of the magnetic field but still too much waste escaping

what is a closed core transformer?

the air and open core combines but still has waste escaping

what is the shell type transformer?

a closed shell & the most efficient

magnetic field is 95% utilized/efficient

what contributes to power loss

1-copper (conductor resistance)

2-hysteresis-rearranging magnetic domains

3-eddy current-swirling currents in the core, lamination of plates helps minimize power loss in this

practice/study last slide of pt 2