Download Activity 3: Electric potential and potential energy

Physics E-1bx: Lecture 1
January 27, 2015
Activity 3: Electric potential and potential energy
•
We can summarize the previous activity as follows:
The potential energy is equal to the mass times the gravitational potential.
•
Now we will define a quantity called the electric potential, which we will give the
symbol V. It is also a scalar field, defined at every point in space:
V(x, y, z) = the electric potential
The SI unit for electric potential is the volt (V).
•
The electric potential is much like the gravitational potential. You can use it to find the
potential energy:
If an object has charge Q at a location where the electric potential is V, then the object
has electric potential energy equal to:
Uelec = QV
1.
The SI unit of charge is the coulomb (C). Find an expression for volts in terms of
coulombs and other basic SI units. (Hint: what is the SI unit of energy?)
2.
You have a 9-volt battery. If you define the electric potential at the (–) terminal to be 0
volts, what would be the electric potential at the (+) terminal? (Not a trick question!)
(+)
(–)
3.
Suppose we define the electric potential at the (–) terminal as –20 volts. Then what will
be the potential at the (+) terminal? Does the value of the electric potential matter?
6