Physics STPM Semester 2 Chapter Capacitor

The capacitance of a variable capacitor can be varied from 250 $\mu$ F to 3750 $\mu$ F. The capacitance of the capacitor is set at 2000 $\mu$ F, and is connected to a power source of l2V. The power source is then removed. What is the maximum potential difference achieved if the capacitance of the capacitor is varied again?

• 6.4V
  
  

• 12 V

• 23 V

• 96 V

Two identical capacitors, X and Y, which are connected in parallel to a battery are shown in the diagram above. When switch S is opened, the potential difference across X is V, the charge stored in Q and Y is uncharged. When switch S is closed, what is the potential difference across Y and the charge stored in Y?

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A capacitor of two parallel conducting plates which are separated by a piece of dielectric, is fully charged by a battery as shown in the diagram above. The capacitance of the capacitor will change if

• different dielectric is used

• the capacitor is not fully charged

• the battery of different voltage is used

• the conducting plates of different metals are used

A capacitor consists of two parallel plates in which the distance between the plates can be adjusted. The capacitor is charged by connecting the capacitor to a battery, which is then removed.The potential diiference between the plates of the isolated capacitor can be increased by

• touching the two Plates

• bringing the two Plates closer

• separating the two plates further apart

• allowing the potential difference increasing by itself

A parallel plate capacitor with dielectric is shown in the diagram above. The charges on the capacitor plates are +Q and -Q. Which statement is not true about the capacitor?

• The electric field within the dielectric is uniform.

• The electric field between the plates is dependent on the net surface charge density.

• The induced charges on the surface of the dielectric are equal in magnitude to the charges of the capacitor plates.

• The electric field due to the induced charges is in the opposite direction to the electric field due to the charges on the capacitor plates.

A dielectric is inserted into an air-filled parallel plate capacitor of capacitance 20  $\mu$  F so that only half of the space between the plates is filled as shown in the diagram above. If the dielectric constant is 5.0, what is the final capacitance of the capacitor?

• 8.3  $\mu$  F

• 30  $\mu$  F

• 60  $\mu$  F

• 100  $\mu$   F

A parallel-plate capacitor is initially charged by a battery and the battery is then disconnected. When the dielectric is removed from the charged capacitor,

• the charge stored in the capacitor increases

• the energy stored in the capacitor increases

• the potential difference between the plates decreases

• the electric field strength between the plates decreases

A capacitor with an air gap between the plates is connected to a battery. The battery is then removed from the capacitor. A dielectric is then used to fill in the air gap between the plates. Which statement is true about the capacitor with the dielectric?

• The energy stored in the capacitor increases.

• The charge stored in the capacitor decreases.

• The potential difference across the plates of the capacitor decreases.

• The electric field strength between the plates of the capacitor increases

Two capacitors which have the same capacitance can be connected in series or parallel. Which statement is true about the charge stored for the same d.c. voltage supply?

• The series connection stores an amount of charge twice that of the parallel connection.

• The parallel connection stores an amount of charge twice that of the series connection.

• The series connection stores an amount of charge four times that of the parallel connection.

• The parallel connection stores an amount of charge four times that of the series connection.

A parallel plate capacitor is fully charged. When an insulator is inserted into the space between the plates of the capacitor, the energy stored in the capacitor decreases by 73.0 %. What is the value of the dielectric constant of the insulator?

• 1.37

• 1.88

• 3.70

• 13.7