How do we get charges to
do what we want them to
do?
Electric Potential Energy
Voltage
Current
Resistance
What happens to PEG?
Was work done on the
ball?
What happens to PEG?
What happens to KE?
Consider the following…
Energy of a particle due to its position
within an electric field
 EPE is a form of mechanical energy
 When a charged particle is moved within
an electric field, work is done and the
energy of that particle changes

Electric Potential Energy
+
Any
change in
EPE?
E
+
+
+
+
+
EPE is
increased
-
EPE decreased
KE increases
Consider the following:
-

When work is done against the electric
field, EPE is increased
◦ Positives closer to other positives
◦ Negatives closer to other negatives
◦ Positives farther from negatives

This particle now has more ability to move
or change matter by virtue of its position
within the electric field
Electric Potential Energy
Strong Electric Field
Weak Electric Field
Which one will increase the EPE of
the charge more?
Potential Difference tells the ability of an
electric field to change the EPE of a
positive charged particle or…
 The difference in EPE of charged particles
at different places in an electric field

Potential Difference / Voltage

SI unit = Volt (V)
◦ 1 𝑣𝑜𝑙𝑡 =
1 𝐽𝑜𝑢𝑙𝑒
1 𝐶𝑜𝑢𝑙𝑜𝑚𝑏
◦ A charge of one coulomb that experiences a
potential change of 1 volt will gain 1 joule of
energy
Potential Difference / Voltage
As electrons travel through
bulb, EPE turned into light
& heat
The potential difference
(orelectrons
By the time
voltage) of the
get battery
back to battery, all
measures the EPE
difference
turnedininto other
EPE of electrons at each
forms
terminal
As electrons
move within the
wire, EPE
turned into KE
Electrons move
within the field
inside the
battery → gain
EPE
Definition of Current

Current is defined as the rate at which
electric charges pass through a certain
area of a conductor
Current is the movement of charge
carriers (+/- charges)
 Current is usually a flow of electrons
(especially in metals)
 Charges are moved by an electric field
(which causes a force)

What is current?
-
Current (I)

𝐼=
∆𝑞
∆𝑡

1 𝐴𝑚𝑝𝑒𝑟𝑒 =
The rate of charge movement
 SI Unit: Ampere (A)

1 𝐶𝑜𝑙𝑜𝑢𝑚𝑏
1 𝑠𝑒𝑐𝑜𝑛𝑑
Electrons flow in one direction only
 Usually supplied by batteries and some
types of generators
 A potential difference increases the EPE,
which is then converted into other forms
(especially kinetic)

Direct Current (DC)


Electrons flow in
both directions,
switching rapidly
(based on the
frequency)
AC is produced by
generators spinning
coils of wire in a
magnetic field,
which produces a
current
Alternating Current (AC)
Current vs. Voltage
Current vs. Voltage
Current vs. Voltage
Current vs. Voltage

Behavior is based on how tightly electrons
are held to individual atoms
Conductors & Insulators

The impedance to charge flow through a
material
◦ How hard is it to make charges move through
the material

Some materials allow charges to flow
more easily than others, based on the
previously stated factors
Resistance



Resistance is the
relationship
between applied
voltage and the
resulting current
SI Unit: Ohm (Ω)
1 𝑂ℎ𝑚 (Ω) =
1 𝑉𝑜𝑙𝑡
1 𝐴𝑚𝑝
Resistance

𝑅=
Δ𝑉
𝐼
The equation for resistance can be
rewritten in the following form:
 𝑉 = 𝐼𝑅
 This is known as Ohm’s Law

◦ Resistance is not dependent on the voltage
Ohm’s Law

Below certain temperatures, some
materials have the ability to conduct
currents with no resistance
Superconductivity