Quiz of capacitor and AC current

• 71,12 C

Three capacitors each of capacitance 9 pF are connected in series.

What is the total capacitance of the combination and the potential difference across each capacitor if the combination is connected to a 120 𝑉 supply?

A 12 𝑝F capacitor is connected to a 50 𝑉 battery. How much electrostatic energy is stored in the capacitor?

A parallel plate capacitor with air between the plates has a capacitance of 8 pF. What will be 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 6?

• 100 pF

• 0.96 pF

• 0.1 pF

Three capacitors of capacitances 2 pF,3 pF and 4 pF are connected in parallel. what is the total capacitance of the capacitors?

• 9pF

• 2pF

• 1pF

• 1/9 pF

Direct current is where the electrons move in _____ direction. 

It is produced by ___________________. 

In an _____________ current, the electrons rapidly change ______________. 

____________________ has an alternating current.

The mains voltage is _________ and has a _______________ of 50Hz. 

This means that the ____________ change direction 50 times every _________.

A 1.5 kW heater is connected to a domestic supply, which is quoted at 240 V, calculate the peak current in the heater and its resistance

• 8.8 A, 3.8 ohm

• 44 A, 1.8 ohm

• 8 A, 38 ohm

• 6.3 A, 3.8 ohm

A transformer is being used with an alternating supply of 240 V to power a lamp rated as 12V, 3A. The secondary coil of the transformer has 80 turns, calculate the number of turns and current for the primary coil.

• 1600 turns

  0.15 A

• 1400 turns

  0.15 A

• 160 turns

  15 A

• 16000 turns

  0.015 A

The primary winding of an electric train transformer has 400 turns and the

secondary has 50. If the input voltage is 120V(rms) what is the output voltage?

• 15 V (rms)

• 30 V (rms)

• 60 V (rms)

• 2.4 V

Using the graph and the equation for alternating current, calculate the value of the current at a time 0.48 s.

• -16A

• 16A

• -13A

• 13A