A $400\mu \mathrm{F}$ capacitor is charged using a $20 \mathrm{V}$ battery. It is connected across the ends of a $600\Omega$ resistor with $20 \mathrm{V}$ potential difference across its plates.

(c) Calculate the time it takes the charge on the capacitor to fall to $2.0\mathrm{mC}$.

A $400\mu \mathrm{F}$ capacitor is charged using a $20 \mathrm{V}$ battery. It is connected across the ends of a $600\Omega$ resistor with $20 \mathrm{V}$ potential difference across its plates.

(d) State the potential difference across the plates when the charge has fallen to $2.0\mathrm{mC}$.

A $4700\mu \mathrm{F}$ capacitor has a p.d. of $12 \mathrm{V}$ across its terminals. Calculate the charge stored on the capacitor.

A $4700\mu \mathrm{F}$ capacitor has a p.d. of $12 \mathrm{V}$ across its terminals. It is connected to a resistor and the charge leaks away through the resistor in $2.5 \mathrm{s}$. Estimate the resistance of the resistor.

A $4700 \mu F$ capacitor has a p.d. of $12 V$ across its terminals. It is connected to a resistor and the charge leaks away through the resistor in $2.5 s$. Suggest why the last two quantities can only be estimates