Ch. 20 Flashcards
(6 cards)
In one region of space the electric potential has a positive constant value. In another region of space, the potential has a negative constant value. What can be said about the electric field within each of these two regions of space?
The electric field is a measure of how much the electric potential changes from one position to another. Therefore, the electric field in each or these regions is zero.
Electric field is related to electric potential by E= -delta V/delta s. This means that the electric field is a measure of change in electric potential with change in position. As the electric potential in each of these two regions is constant with their opposite polarity, the electric field in both regions must be zero.
If the electric field is zero in some region of space is the electric potential zero there as well? Explain.
Not necessarily. The electric field is related to the rate of change of electric potential, not to the value of the electric potential. Therefore, if the electric field is zero in some region of space, it follows that the electric potential is constant in the region. The constant value of the electric potential may be zero, but it may also be positive or negative.
No, not necessary. The electric field is a measure of change in position. Therefore the electric field is zero in cases; A) when electric potential is constant and B) when electric potential is zero. So electric potential need not necessarily be zero. If the electric field is zero, potential may be positive or negative.
Sketch the equipotential surface that goes through point one. Repeat for point 2 and three.
Draw a line through all three points, straight down.
How much work is required to move a charge from one location on an equipotential to another point on the same equipotential? Explain.
Zero. The electric field is perpendicular to an equipotential, therefore the work done in moving along an equipotential is zero.
Since the potential difference in the equipotential surface is zero, the work done for a moving charge in that surface is 0. Because W=q x delta V. Delta V is zero.
A capacitor is connected to a battery and fully charged. What becomes of the charge on the capacitor when it is disconnected from the battery? What becomes of the charge when the two terminals of the capacitor are connected to one another?
When the capacitor is disconnected from the battery, the charge on the capacitor plates simply remains where it is– there is no way for it to go anywhere else. When the terminals are connected to one another the charges flow from plate to plate until both plates have zero charge.
On which of the following quantities does the capacitance of a capacitor depend: a) the charge on the plates; b) the separation of the plates; c) the voltage difference between the plates; d) the electric field between the plates; or e) the area of the plates?
It is based on the separation of the plates and the area of the plates because C= E0xA/d
