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WorksheetsPre-U Capacitors
Total questions: 14
Worksheet time: 22mins
Two plates hold identical and opposite electric charges, +Q and -Q, and are separated by a distance d. What is the electric potential at the mid-point between these two plates?
2Q
Q / d
2Q / d
zero
Capacitors are made using 'dielectric materials'. Which of these statements best describes a dielectric material?
A conductor that can be polarised
A conductor that cannot be polarised
An insulator that can be polarised
An insulator that cannot be polarised
A simple capacitor of capacitance C is produced using 2 parallel plates of area A and separation d. (Air is used as the dielectric material). If the separation of the plates is halved to d/2 and the area of both plates is doubled, the new capacitance will be:
C
2 C
4 C
8 C
A 10-4 F capacitor is connected to a 10 V cell. What is the charge and energy stored on the capacitor?
A
B
C
D
Two large capacitors of value 1 F and 2 F are wired in series and then in parallel. What is the total capacitance when combined like this?
A
B
C
D
Identical capacitors are connected in different combinations. Which of these capacitor networks has the largest capacitance?
A
B
C
D
The formula τ = RC can be used to find the time constant for the discharge of a capacitor through a resistor. The capacitor is initially charged to a potential of 1 V.
At a time t = τ, what is the voltage in volts across the capacitor?
e
e-1
0.5
0
Which of the following graphs best shows the potential difference across a capacitor discharging through a resistor?
A
B
C
D
Which of the following graphs best shows the potential difference across a capacitor charging through a resistor?
A
B
C
D
The energy stored in a capacitor is E when charged to a voltage V0. After a time τ the potential difference across the capacitor has fallen to 0.69 V0 as it discharges through a resistor. This means that the energy transferred to the resistor in this time will be:
0.31 E
0.692 E
(1 - 0.692) E
0.312 E
A capacitor discharges through a fixed resistor. The time constant τ for the capacitor and resistor is 10 seconds. At what time will the charge across the capacitor have dropped to half the original value?
0.5 e-10
10 e-0.5
10 ln(-0.5)
-10 ln(0.5)
A capacitor X of capacitance C is charged by connecting it, with a movable lead, to a battery of emf E.
The lead is moved so that capacitor X is first disconnected from the battery and then connected to a second capacitor Y of capacitance C.
What is the energy stored in capacitor Y?
1/8 CE2
1/4 CE2
1/2 CE2
CE2
In a hydrogen atom, the electron is considered to be a distance of 5.3 x 10-11 m from the proton. What is the size of the electrostatic force on the electron at this distance?
5.1 x 1011 N
27 N
8.2 x 10-8 N
2.7 x 10-21 N
A capacitor discharge circuit of time constant 45 ms includes a capacitor and resistor. The capacitor has a capacitance of 18 µF.
What is the resistance of the resistor?
2.5 x 103 Ω
2.5 Ω
0.40 Ω
4.0 x 10-4 Ω
