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U5. L3. Electric Potential Difference
SHOW ALL WORK USING GUESS. No GUESS, no credit. Box final answers and write them in a sentence.
Examples
1. A positive test charge of 1.0 x 10-6 C is in an electric field created by charged parallel plates that exerts a force of 2.0 x 10 -4 N
on it. If the plates are 5cm apart, what is the voltage?
Guided practice
1.
A positive test charge of 4.0 x 10-6 C is in an electric field that exerts a force of 2.3 x 10-4 N on it. If the positive and negative
plates are 10 cm apart, what is the voltage? (Answer: ΔV = 5.75 V)
2.
A uniform electric field is established by connecting the plates of a parallel-plate capacitor to a 12-V battery.
a. If the plates have a separation of 0.75 cm, what is the magnitude of the electric field in the capacitor?
(Answer: E = 1600 V/m)
b.
A charge of 6.24 x 10-6 C moves from the - plate to the + plate. Find the amount of work done on the charge.
(Answer: W = 7.5 x 10-5 J)
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3.
A parallel plate capacitor is a device that when hooked up to a battery can store electrical energy between its two metal
plates by separating charge so that one plate is more positively charged than the other. This creates an electrical field
between the plates. Air separates the two metal plates as they charge and since air is a good insulator it keeps the plates
from discharging until it is necessary to do so. When a capacitor releases the electrical energy that has been stored, it
usually does so very quickly. An example of this is the flash on a camera. The flash is a capacitor that charges when it is not
in use and then releases all of its electrical energy in a split second when taking a picture. This allows for such an intense
flash of light to occur.
Let’s say that a parallel plate capacitor has plates that are separated by 0.75 mm. If the electric field between the plates
has a magnitude of 1.2 x 105 V/m, what is the potential difference between the plates? (Answer: ΔV = 90 V)
4.
The gap between electrodes in a spark plug is 0.060 cm. Producing an electric spark in a gasoline-air mixture requires an
electric field of 3.0 x 106 V/m. What minimum potential difference must be supplied by the ignition circuit to start a car?
(Answer: ΔV = 1800 V)
5.
An electron is moved through an electric potential difference of 450 V. How much work is done on the electron?
(Answer: W = 7.2 x 10 -17)
INDEPENDENT PRACTICE
1.
Draw the set-up of a uniform electric field.
2.
What does voltage mean?
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3.
In a circuit, 150 J of heat energy (work) is produced when 0.3 C of charge passes through it. What is the voltage of the
battery that is hooked up to the circuit?
4.
A 6V battery is connected to two plates as shown in the figure below. The distance between the plates is 0.25m. Suppose
0.2 C of charge is moved through the plates. Find:
a.
The amount of work done in moving this charge
b.
The force exerted on the charge
c.
The electric field strength
Created by M. Kelly
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