Units
Devices
Details
Equations
Problems
100
Convert 6 mm to m
.006m
100
Draw a label a parallel plate capacitor connected to a battery
two oppositely conducting charged plates with a insulator (dielectric) in between
100
Does the charge vary directly or inversely with the voltage?
directly
100
What is an equation for capacitance which involves charge and change in the voltage?
C = q/V
100
If you increase the potential difference between the plates of a capacitor, what happens to (a) the amount of charge on each plate?
the charge increases
200
The unit of capacitance
Farad
200
Name 3 devices which use a capacitor
answers may vary, but the three listed in the reading are camera flashes, defibrillator, radio tuner
200
What are two factors which determine capacitance?
the geometry of a capacitor and the nature of its insulator
200
What is an equation for capactance which includes distance?
C = (ε0 * A)/d
200
A capacitor accumulates 6.4e−5 C of charge when connected to a 9.0 volt battery. What is its capacitance?
7.1e−6 F
300
Who was the unit of capacitance named in honor of?
Michael Faraday
300
Why is a capacitor used in a radio tuner?
Because it takes a fixed amount of time to charge or discharge a given capacitor, capacitors are used in circuits where timing is essential
300
What is A in the cpacitance formula?
The Area of one plate
300
What is the potential energy formula for capacitance which includes charge?
PE = q2/(2c)
300
Two circular metal plates with area 0.28 square meters are placed 1.6e−3 m apart to form a parallel-plate capacitor. Find its capacitance
1.5e−9 F
400
Convert 600 microfarads (μF) to Farads
0.0006 Farads
400
How does a capacitor in a computer keyboard work
As you press down on a key, the two plates of its capacitor are pushed closer together. Since this changes the geometry of the capacitor, it also changes the capacitance: Specifically, it increases it. A microprocessor in the keyboard interprets the change in capacitance as a signal that the key has been pressed.
400
What is the name for εo
permittivity constant
400
What is the potential energy formula for capacitance which includes voltage?
PE = (C *ΔV2)/V
400
Find Potential energy when C =0.0015 μF and ΔV = 25,000 V
PEe = 0.47 J
500
Convert 0.44 picofarads (pF) to farads
4.4 x 10^-13 F
500
Why are the back panels of televisions are labeled with warnings against attempting to disassemble them yourself?
The stored energy in a TV capacitor can give you a dangerous shock, even after the set is unplugged.
500
Do electrons move across the gap between the plates? (explain)
No, they move away from one plate, leaving a net positive charge behind, and go toward the other plate, which takes on a negative charge.
500
Given charge, voltage, area of one plate, how do you determine the distance between the plates?
d=(ε0 * A*V)/q
500
A battery will produce a ΔV of 175 V across the plates. Set the distance between them to produce a charge of 2.00 nC. The area of one plate is 0.010 m2. Remember ε0 = 8.85×10−12 C2/N∙m2 and a nC = 10-9 C. Find the distance in mm.
7.74mm
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