Answer:

Which set-up is brighter?

• In a series circuit, the voltage is equally distributed among all of the bulbs. Bulbs in parallel are brighter than bulbs in series. In a parallel circuit the voltage for each bulb is the same as the voltage in the circuit.

What happens when the number of dry cells was increased?

• Adding dry cells in series increases the voltage in a circuit. ...  Adding dry cells increases the current in a circuit as shown by the ammeter readings  Brightness of the bulb also indicates the amount of current passing through it.  The bigger the current through the bulb, the brighter it glows.