Capacitance of A Capacitor

A 400 μF capacitor is charged so that the voltage across its plates rises at a constant rate from 0 V to 4.0 V in 20 s. What current is being used to charge the capacitor?

• 5 μA

• 20 μA

• 40 μA

• 80 μA

The graph shows how the charge stored by a capacitor varies with the pd applied across it. Which line, A to D, in the table gives the capacitance and the energy stored when the potential difference is 5.0 V?

• capacitance= 2.0 μF

  energy stored = 25 μF

• capacitance= 2.0 μF

  energy stored = 50 μF

• capacitance= 10.0 μF

  energy stored = 25 μF

• capacitance= 10.0 μF

  energy stored = 50 μF

A capacitor of capacitance C discharges through a resistor of resistance R. Which one of the following statements is not true?

• The time constant will decrease if C is increased.

• The time constant will increase if R is increased.

• After charging to the same voltage, the initial discharge current will increase if R is decreased.

• After charging to the same voltage, the initial discharge current will be unaffected if C is increased.

Capacitor is a device used to..................

• store electrical energy

• vary the resistance

• store magnetic energy

• dissipate energy

Capacitor stores which type of energy?

• kinetic energy

• vibrational energy

• potential energy

• heat energy

What is the value of capacitance of a capacitor which has a voltage of 4V and has 16C of charge?

• 2F

• 4F

• 6F

• 8F

Three capacitors of 15 μF, 25 μF and 40 μF are connected in parallel across a 250 V supply. Find the amount of energy stored.

• 2.35 J

• 0.235 J

• 2.5 J

• none of the above

The unit of capacitance is:

• Ohm (Ω)

• Farad (F)

• Henry (H)

• Volt (V)

The capacitance of a capacitor depends on:

• The area of its plates

• The distance between its plates

• The material of its plates

• all of the above

In a DC circuit, once a capacitor is fully charged, what happens to the current flowing through it?

• It becomes zero

• It remains constant

• It increases indefinitely

• It oscillates at a high frequency