4/18/2012

1

Electric and Magnetic

Phenomena

Electric and magnetic phenomena

are related and have many practical

applications.

5a

: Direct Current

•

Students know how to predict the voltage or

current in simple direct current (

DC) electric

circuits constructed from batteries, wires,

resistors, and capacitors

.

•

Battery: provides

electric potential

–

Symbol: _________or_________

•

Resistor: slows

current

, changes electrical energy

to

heat

and/or

light

–

Symbol: ______

•

Wires: carry current through a circuit

–

Symbol:

lines

5b: Ohm’s Law

•

Students know how to solve problems

involving Ohm's law.

•

V = I R

–

V:

voltage

–

I:

current

–

R:

resistance

5c: Power

•

Students know any resistive element in a DC

circuit dissipates energy, which

heats

the

resistor. Students can calculate the power (rate

of energy dissipation) in any resistive circuit

element by using the formula P =

VI

=

I

2

R

.

5d: Transistors

•

Students know the properties of transistors

and the role of transistors in electric circuits.

•

Transistors modify

current

–

Often as an

amplifier

•

Transistors are used in

any electronic device

5e: Charges

•

Students know charged particles are sources

of electric fields and are subject to the forces

of the electric fields from other charges.

•

Charges are

negative

(extra electrons) or

positive

(lack of electrons

•

Opposite charges

attract

•

Like charges

repel

4/18/2012

2

5f: Magnetism

•

Students know magnetic materials and electric

currents (moving electric charges) are sources of

magnetic fields

and are subject to forces arising

from the magnetic fields of other sources.

•

North

and

South

Poles

–

Opposites

attract

, likes

repel

•

Moving charges

induce

a magnetic field

•

Magnetic fields

induce a force

on moving charges

5g: Induced Magnetic Field

•

Students know how to determine the direction

of a magnetic field produced by a current

flowing in a straight wire or in a coil.

•

Right Hand Rule

–

Thumb:

straight current in a wire

or

magnetic field in

a coil

–

Curled fingers:

magnetic field around a wire

or

current in a coil

5h: Induced Current

•

Students know changing magnetic fields

produce electric fields, thereby inducing

currents

in nearby conductors.

•

Current can be created in a wire without

anything directly

connected

to it

5i: Plasma

•

Students know plasmas, the fourth state of

matter, contain ions or free electrons or both

and

conduct electricity

.

•

Plasma:

superheated gas

•

Lightning

is plasma of air

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