David Sang and Graham Jones Solutions for Chapter: Capacitance, Exercise 14: EXAM-STYLE QUESTIONS

A capacitor in an electronic circuit is designed to slowly discharge through an indicator lamp. It is decided that the time taken for the capacitor to discharge needs to be increased. Four changes are suggested:

(1) Connect a second capacitor in parallel with the original capacitor.

(2) Connect a second capacitor in series with the original capacitor.

(3) Connect a resistor in parallel with the lamp.

(4) Connect a resistor in series with the lamp.

Which suggestions would lead to the discharge time being increased?

This is a circuit that can be used to measure the capacitance of a capacitor.

The reed switch vibrates back and forth at a frequency of $50 \mathrm{Hz}$. Each time it makes contact with A, the capacitor is charged by the battery so that there is a p.d. of $12 \mathrm{V}$ across it. Each time it makes contact with B, it is fully discharged through the resistor.

Calculate the average current in the resistor.

This is a circuit that can be used to measure the capacitance of a capacitor.

The reed switch vibrates back and forth at a frequency of $50 \mathrm{Hz}$. Each time it makes contact with A, the capacitor is charged by the battery so that there is a p.d. of $12 \mathrm{V}$ across it. Each time it makes contact with B, it is fully discharged through the resistor.

Calculate the average power dissipated in the resistor.

A second capacitor of the same value is connected in series with the first capacitor.

Discuss the effect on both the current recorded and the power dissipated in the resistor.

Explain what is meant by the time constant of a circuit containing capacitance and resistance.

 A circuit contains capacitors of capacitance $500\mu \mathrm{F}$ and $2000\mu \mathrm{F}$ In series with each other and in series with a resistance of $2.5\mathrm{k}\Omega$.

Calculate the effective capacitance of the capacitors in series.

A circuit contains capacitors of capacitance $500\mu \mathrm{F}$ and $2000\mu \mathrm{F}$ In series with each other and in series with a resistance of $2.5\mathrm{k}\Omega$.

Calculate the charge on the capacitor plates when there is a potential difference of $50 \mathrm{V}$ Across the plates.

A circuit contains capacitors of capacitance $500\mu \mathrm{F}$ and $2000\mu \mathrm{F}$ in series with each other and in series with a resistance of $2.5\mathrm{k}\Omega$. Calculate the time taken for the charge on the plates to fall to $5\%$ of the charge when there was a p.d. of $50 \mathrm{V}$ across the plates.