# What happens when an external agent changes charge on a working capacitor?

Consider an uncharged parallel plate capacitor having capacitance 'C' with a resistance 'R' connected to it in series and both of them connected across a ideal cell of emf E volts . If in between the process of charging of capacitor , let us say at that instant the charges on upper and lower plates of capacitors are +q and -q , an external agent comes and gives charge +2q to the lower surface of upper plate (having charge +q already ) . Then what will happen ? .

My prediction : At that very instant when +2q is given to the lower surface of the first plate , the charges will redistribute on the plates so that no field is created inside the conducting plates due to stationary charges . The redistribution is shown here Charges present on outer surface of the plates will have no effect on current .Although due to the changed charges on inner surface of plates potential difference across capacitor will change . And thus current will also change .

Is this correct ?

This explaination seems correct to me but still i have a doubt in my own explaination . Wouldn't the flowing current restrict the redistribution of charges on plates ? The electric field in the plates will be downwards , so wouldn't the downward motion of free electrons to neutralize the given charge and hence redistribute the charge on the plate be restricted ?

So what exactly will happen in this situation ?

Adding charges on capacitor wouldn't change the charge configuration of capacitor at steady state because at steady state $$I =0$$ hence Voltage across capacitor would be equal to emf of battery which implies that charge on capacitor will be equal to $$Q_c = EC$$ where E is Emf of battery.