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Transcript
```Gravitational Potential vs. Gravitational
Potential Energy
Voltage is not the same as electrical
potential energy, because voltage is
potential energy per unit of charge.
Circuits require high potential and low
potential—a potential difference or
Voltage.
Batteries require a voltage…they do
the work that keeps a circuit “flowing”.
Did you find these configurations?
Why are these successful?
For a circuit to “work”:
• There must be an energy supply capable of
doing work on charge to move it from a low
energy location to a high energy location and
thus establish an electric potential difference
across the two ends of the external circuit.
• There must be a closed conducting loop in the
external circuit that stretches from the high
potential, positive terminal to the low
potential, negative terminal.
What is current?
Do you notice a problem?
Conventional Current:
• Ben Franklin, who conducted extensive scientific studies in both
static and current electricity, envisioned positive charges as the
carriers of charge. As such, an early convention for the direction of
an electric current was established to be in the direction that
positive charges would move. The convention has stuck and is still
used today. The direction of an electric current is by convention
the direction in which a positive charge would move. Thus, the
current in the external circuit is directed away from the positive
terminal and toward the negative terminal of the battery. Electrons
would actually move through the wires in the opposite direction.
Knowing that the actual charge carriers in wires are negatively
charged electrons may make this convention seem a bit odd and
outdated. Nonetheless, it is the convention that is used worldwide.
So you have to just get used to it!
When an electrochemical cell no longer works, it is out
of charge and must be recharged before it can be used
again.
b. An electrochemical cell can be a source of charge in a
circuit. The charge that flows through the circuit
originates in the cell.
c. Charge becomes used up as it flows through a circuit.
The amount of charge that exits a light bulb is less than
the amount that enters the light bulb.
T or F
T or F
T or F
d. Charge flows through circuits at very high speeds. This
explains why the light bulb turns on immediately after
T or F
the wall switch is flipped.
e. The local electrical utility company supplies millions
and millions of electrons to our homes everyday.
T or F
What is resistance?
Quantity
Symbol
Equation(s)
Standard
Metric Unit
Other Units
Potential Difference (a.k.a.
voltage)
V
V = PE / Q
V=I•R
Volt (V)
J/C
Current
I
I=Q/t
I=V/R
Amperes (A) Amp or C / s or V / Ω
Power
P
P = Work or
Watt (W)
PE / t
Resistance
R
Energy
E or PE
R=V/I
PE = V • Q
PE = P • t
J/s
Ohm (Ω)
V/A
Joule (J)
V • C or W • s
```
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