Advertisements
Advertisements
Question
When a dielectric slab is gradually inserted between the plates of an isolated parallel-plate capacitor, the energy of the system decreases. What can you conclude about the force on the slab exerted by the electric field?
Solution
As the energy of the system decreases, the change in the energy is negative. Force is defined as a negative rate of change of energy with respect to distance.
`F = -(∂U)/(∂x)`
So, as the energy decreases, the force due to the electric field of the capacitor increases when the dielectric is dragged into the capacitor.
APPEARS IN
RELATED QUESTIONS
What meaning would you give to the capacitance of a single conductor?
Four capacitors, C1, C2, C3 andC4 are connected as shown in Figure 3 below. Calculate equivalent capacitance of the circuit between points X . and Y.
Net capacitance of three identical capacitors in series is 2 μF. What will be their net capacitance if connected in parallel?
Define the dielectric constant of a medium. What is its S.I unit?
Two parallel uniformly charged infinite plane sheets, '1' and '2', have charge densities + `sigma and -2sigma `respectively. Give the magnitude and direction of the net electric field at a point.
(i) in between the two sheets and
(ii) outside near the sheet '1'.
A parallel plate capacitor is charged and then disconnected from the charging battery. If the plates are now moved farther apart by pulling them by means of insulating handles, then ______.
Two metal plates are separated by 2 cm. The potentials of the plates are -10 V and + 30 V. The electric field between the two plates is ______.
Capacity of a parallel plate capacitor with a medium of dielectric constant 8 is 12 µF. If the medium is removed, then capacity of the capacitor would be ____________.
A parallel plate air capacitor is charged to a potential difference of V volts. After disconnecting the charging battery the distance between the plates of the capacitor is increased using an insulating handle. As a result the potential difference between the plates ______.
A free electron and a free proton are placed between two oppositely charged parallel plates. Both are closer to the positive plate than the negative plate.
Which of the following statements is true?
- The force on the proton is greater than the force on the electron.
- The potential energy of the proton is greater than that of the electron.
- The potential energy of the proton and the electron is the same.
A parallel plate capacitor with air between the plates has a capacitance of 8 pF. Calculate the capacitance if the distance between the plates is reduced by half and the space between them is filled with a substance of dielectric constant. (εr = 6)
The energy required to charge a parallel plate condenser of plate separation d and plate area of cross-section A such that the uniform electric field between the plates is E is:
A parallel plate air capacity 'C' farad, potential 'V' volt and energy 'E' joule. When the gap between the plates is completely filled with dielectric ______.
Two infinitely long parallel conducting plates having surface charge densities +σ cand -σ respectively are separated by a small distance. The medium between the plates is a vacuum. If ε0 is the dielectric permittivity of the vacuum, then the electric field in the region between the plates is ______.
The equivalent capacitance between the point A and B as shown in figure will be ______.
