Physics
Capacitors and Capacitance
189 Questions
Capacitors and capacitance are crucial topics in physics, covering the storage of electric charge and energy. These concepts explore series and parallel combinations, dielectric materials, and capacitive reactance. Questions frequently appear in various competitive engineering and medical entrance exams.
Series and parallel capacitorsParallel plate capacitorsCapacitive reactance formulasDielectrics and permittivitySpherical capacitors
Capacitors and Capacitance Questions
The capacitance of a capacitor is:
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The ability of a capacitor to store charge
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The amount of charge stored on a capacitor
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The ratio of charge to voltage on a capacitor
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All of the above
C
Correct answer
Explanation
The capacitance of a capacitor is the ratio of charge to voltage on a capacitor.
The capacitive reactance of a capacitor is:
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Directly proportional to frequency
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Inversely proportional to frequency
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Independent of frequency
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Dependent on the capacitance value
B
Correct answer
Explanation
Capacitive reactance decreases with increasing frequency, as the capacitor opposes the change in voltage more strongly at higher frequencies.
What is the relationship between permittivity and capacitance?
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Permittivity is directly proportional to capacitance
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Permittivity is inversely proportional to capacitance
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Permittivity is independent of capacitance
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Permittivity is inversely proportional to the square of capacitance
A
Correct answer
Explanation
Permittivity and capacitance are directly proportional, meaning that as permittivity increases, capacitance also increases.
What is the typical voltage range of a supercapacitor?
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1-2 V
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12-24 V
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220-240 V
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440-480 V
A
Correct answer
Explanation
Supercapacitors typically operate at low voltages, typically ranging from 1 to 2 volts.
What is the relationship between permittivity and capacitance?
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Permittivity is directly proportional to capacitance
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Permittivity is inversely proportional to capacitance
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Permittivity is independent of capacitance
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Permittivity is equal to capacitance
A
Correct answer
Explanation
Permittivity and capacitance are directly proportional, meaning that a material with a higher permittivity will have a higher capacitance.
The capacitance of a capacitor is:
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The ratio of charge to voltage.
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The ratio of voltage to charge.
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The product of charge and voltage.
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The quotient of charge and voltage.
A
Correct answer
Explanation
The capacitance of a capacitor is defined as the ratio of charge to voltage.
The energy stored in a capacitor is:
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The product of voltage and charge.
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The quotient of voltage and charge.
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The difference of voltage and charge.
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The sum of voltage and charge.
A
Correct answer
Explanation
The energy stored in a capacitor is the product of voltage and charge.
What is the formula for the reactance of a capacitor?
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$X_C = 1/(2\pi fC)$
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$X_C = 2\pi fC$
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$X_C = 1/(2\pi fL)$
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$X_C = 2\pi fL$
A
Correct answer
Explanation
The reactance of a capacitor ($X_C$) is given by the formula $X_C = 1/(2\pi fC)$, where $f$ is the frequency and $C$ is the capacitance.
What is the relationship between the permittivity of a dielectric material and its capacitance?
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Directly proportional
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Inversely proportional
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No relationship
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Logarithmically proportional
A
Correct answer
Explanation
The capacitance of a dielectric material is directly proportional to its permittivity.
Which of the following factors does NOT affect the capacitance of a parallel-plate capacitor?
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Plate area
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Plate separation
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Dielectric material
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Applied voltage
D
Correct answer
Explanation
The capacitance of a parallel-plate capacitor is independent of the applied voltage.
Gauss's Law can be used to calculate the capacitance of a parallel-plate capacitor. What is the capacitance of a parallel-plate capacitor with plate area A and separation d?
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C = ε0A/d
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C = ε0d/A
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C = A/ε0d
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C = d/ε0A
A
Correct answer
Explanation
The capacitance of a parallel-plate capacitor is given by C = ε0A/d, where ε0 is the permittivity of free space, A is the area of the plates, and d is the separation between the plates.
The capacitance of a capacitor is directly proportional to the:
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Area of the plates
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Distance between the plates
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Permittivity of the dielectric material
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All of the above
D
Correct answer
Explanation
The capacitance of a capacitor is directly proportional to the area of the plates, the permittivity of the dielectric material, and inversely proportional to the distance between the plates.
The energy stored in a capacitor is given by:
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$E = rac{1}{2}CV^2$
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$E = rac{1}{2}LI^2$
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$E = rac{1}{2}QV$
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$E = rac{1}{2}FI$
A
Correct answer
Explanation
The energy stored in a capacitor is given by $E = rac{1}{2}CV^2$, where C is the capacitance and V is the voltage across the capacitor.
What is the relationship between inductance and capacitance in an AC circuit?
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Inductance and capacitance are directly proportional
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Inductance and capacitance are inversely proportional
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Inductance and capacitance are independent of each other
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None of the above
B
Correct answer
Explanation
Inductance and capacitance are inversely proportional in an AC circuit. This means that as the inductance of a coil increases, the capacitance of the circuit decreases, and vice versa.
The capacitance of a parallel-plate capacitor is directly proportional to:
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Area of the plates
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Distance between the plates
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Permittivity of the material between the plates
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All of the above
D
Correct answer
Explanation
The capacitance of a parallel-plate capacitor is directly proportional to the area of the plates, inversely proportional to the distance between the plates, and directly proportional to the permittivity of the material between the plates.