Chapter 13 Capacitance

Which procedure below will increase the capacitance of a parallel-plate capacitor?

• Increase the distance of separation between the two plates

• Reduce the surface area of the plate

• Insert an insulator between the two plates

• Insert a conductor between the two plates

A parallel-plate capacitor is charged and then disconnected from the supply. Which of the following will increase the capacitance of the capacitor?

• Reduce the area of the plates

• Move the plates closer to each other

• Insert a conductor between the plates of the capacitor

• Increase the potential difference across the capacitor

An air-filled capacitor C consists of two parallel plates, each of area A and separated by a distance d. A dielectric with relative permittivity 5 is then inserted between the two plates. What is the new capacitance of the capacitor?

• $\frac{1}{5}C$

• $\frac{1}{25}C$

• 5C

• 25C

A capacitor is charged by a constant current of 4.0 mA for 0.80 s. If the potential difference across the capacitor is 320 V, what is the capacitance of the capacitor?

• 5.0 $\mu F$

• 10 $\mu F$

• 13 $\mu F$

• 32 $\mu F$

A parallel-plate capacitor of cross-sectional area A is connected across a battery of potential difference V. A dielectric is then inserted into the capacitor. If the relative permittivity of the dielectric is 2.5 and the distance of separation between the plates is 0.050 mm, calculate the ratio of charge on the capacitor without the dielectric to the charge on the capacitor with dielectric.

• 2:5

• 5:2

• 1:4

• 1:2

Two uncharged capacitors of capacitance 2.0 $\mu F$  and 4.0 $\mu F$  are connected in parallel with a battery of e.m.f., E and negligible resistance as shown in the diagram. After 20 s, the ammeter reads 3.0 $\mu A$  . What is the value of e.m.f.E?

• 60 V

• 40 V

• 20 V

• 10 V

A capacitor is connected in series with a light bulb and a voltage supply as shown in the diagram. If a dielectric is inserted between the parallel plates of the capacitor, which statement is not true about the capacitor?

• The potential difference across the capacitor remains constant.

• The electric field strength between the plates increases at the moment the dielectric is inserted.

• The charge on the capacitor increases.

• The capacitance of the capacitor increases.

An uncharged capacitor of capacitance 8.0 $\mu F$  is connected to a battery of e.m.f. V and negligible internal resistance. If the charge on each plate of the capacitor is 24 $\mu C$  , what is the value of V?

• 3.0 V

• 6.0 V

• 10 V

• 14 V

Nine capacitors are arranged in a circuit as shown in the diagram. Which section of the circuit provides the lowest capacitance?

• PQ

• PR

• ST

• TU

Two capacitors of capacitance 3 $\mu F$  and 2 $\mu F$  are connected in series with the battery as shown in the diagram. If  $V_1$  and  $V_2$  are the potential difference across the capacitors of  3 $\mu F$  and 2 $\mu F$  respectively, what is the ratio of  $\frac{V_1}{V_2}$  ?

• 3:2

• 3:1

• 2:1

• 2:3