Transcript Electric Charge

Electric Charge
Spectra of Science
Amole
2015
What causes electric charge?


All matter is made of atoms
Atoms contain:
◦ Protons- Positive
+
◦ Electrons- Negative
-
◦ Neutrons- Neutral/ No charge
0

An unequal amount of (+) and (-) makes
a material “charged”

Electric Charge is measured in
coulombs (C)
What is electric force?

Objects with opposite charges (one
negative, one positive) will attract
each other.
+

-
Objects with like charges (both
negative or both positive) will repel
each other.
+
+
- -
What affects electric force?

Charge
◦ More charge = greater force

Distance
◦ Greater distance = weaker force

Does not require contact due to their
electric field
+
-
How do objects become
charged?

(+) and (0) are
relatively fixed in
the nucleus, but (-)
in the outer parts
of atom can be
transferred
between objects.

If the nucleus were
a size of a marble,
the whole atom is
the size of a
football stadium
How do objects become
charged?

Charging by friction
◦ rubbing or sliding

Charging by contact
◦ touching

Induced charge
◦ Charge brought near object
Charge Demos
-Magnets-Electric force;
Distance & charge
-Magic wand-friction
-2 balloons
-Balloon & wall-induced
-Door knob-contact
-Plasma ball-Electric field
Current and
Circuits
Spectra of Science
Amole
2015
What is a circuit?
A set of electrical components that
supply one or more paths for
movement of charges
 Open- incomplete/broken path
 Closed- complete/continuous path

What is current and resistance?

Current: The rate that electric
charges move through a conductor

Resistance: opposition posed to a
circuit (slows down current)
What causes current?
Electrical potential energy- energy
charges have due to position in the
electric field
 Affected by distance and type of
force
 Measured in joules (J)

Low PE
High PE
+ +
+ -
-
+
-
What causes current?
Forces can be used to push charges
in the opposite direction on the
electric force to create…
 Potential Difference –change in
electrical PE
 Measured in volts
 Often referred to as
voltage
 Batteries can
supply this

What is a series and parallel
circuit?

Series- same loop
◦ All resistors on same
loop experience
same amount of
current

Parallel- multiple
loops
◦ current splits up
among the loops
with the individual
loop currents
adding to the total
current
What is a series circuit?

One path
All resistors on same
loop
 Experience same
current through all
devices
 Resistance may
differ
 Voltage can be
different

V = IR
R = V/I
What is a parallel circuit?

Multiple paths

All resistors on own
loop
Same voltage
Can have different
currents through
each device
Individual loop
currents add up to
create the total
current
Resistance may
differ




V = IR
R = V/I
What are schematic diagrams?

A way to draw circuits using symbols
What are schematic diagrams?

A way to draw circuits using symbols
Series
Parallel
Circuit Activity
Use students to create
circuits:
-open
-closed
-series
-parallel
How do I measure A, V, Ω?

Current
◦ measure amperes (A)
◦ use ammeter

Voltage◦ measure volts (V)◦ use voltmeter

Resistance
◦ measure Ohms (Ω)
◦ Use ohmmeter (on multimeter)
◦ use ohm’s Law equation: V = IR
How do I measure A, V, Ω?
A
multimeter will measure all
values by simply selecting on the
dial
What are conductors and
insulators?
Conductor – a material in which
charges move freely and can carry
electric current
 Low resistance

Insulator - a material in which
charges cannot move freely and does
not easily carry electric current
 High resistance

Conductors and
Insulators
Build simple series circuit
Test:
- paperclip
- penny
- nickel
- foil
- index card
- wood stick
- string
- plastic stick