In the following experiment, we will explore the factors that depend on the brightness of a light bulb in a simple circuit. We will find that the brightness depends on several factors, such as: the number of bulbs, the voltage at the circuit terminals. The voltage at the circuit terminals can be increased by connecting batteries of increasingly higher voltages or by connecting several batteries in series. In order for the bulbs not to burn out, the applied voltage must not exceed the nominal voltages that are written on them.