Electric Potential
What is another (more common) name for electric potential?
Voltage
What are the units of electric potential energy?
Joules (like all other forms of energy)
What are the units of capacitance?
Farads
Is electric potential a measurement of the interaction between two particular charges, or of how a charge affects the space around it?
How a charge affects the space around it
Is electric potential energy a measurement of the interaction between two particular charges, or of how a charge affects the space around it?
The interaction between two particular charges
What is a capacitor and how is a capacitor constructed?
A capacitor is a device that stores electric charge and electric potential energy. A capacitor is constructed with two conducting plates separated by a dielectric material.
Give at least two differences between electric force, electric field, electric potential energy, and electric potential.
(various answers)
If a negative charge is initially at rest in an electric field, will it move toward a region of higher voltage or lower voltage? What about a positive charge? How does the electric potential energy of the charge change in each case?
Negative charges move from low voltage to high voltage. Positive charges move from high voltage to low voltage. In both cases, electric potential energy decreases (U = qV).
Give at least two purposes that a dielectric material serves in a capacitor.
1) Prevents the flow of charges between the conducting plates
2) Increases capacitance
If the electric potential at a point is zero, does that mean that the electric field is also zero? Why/why not?
No, because electric field is determined by the difference in voltage between two points (a derivative). If the voltage at one point is zero, that is not enough information to determine electric field.
A 3000 pF capacitor stores 50 μC of charge. How much energy is stored?
0.42 J
How strong is the electric field between the plates of a 22.0-μF air-gap capacitor if they are 0.1 mm apart and each has a charge of 40 μC?
182 V/m
What is the electric potential 15.0 cm from a 4.00-μC point charge?
2.4*105 V
Two identical -10-μC point charges are initially spaced 7.0 cm from each other. If they are released at the same instant from rest, how fast will they be moving when they are very far away from each other? Assume they have identical masses of 2 mg. Use conservation of energy.
2535 m/s
A capacitor is constructed from steel plates separated by 4 mm of plexiglass (K = 3.4). What must the area of these plates be if the capacitor is to store 0.001 J of energy when charged to 1500 V?
0.12 m2