Every light fixture has a maximum wattage for each fixture written on it. This tells you the maximum amount of wattage allowed to safely use that fixture. A higher wattage bulb can cause a fire because of the amount of heat the bulb produces.
In order to figure out how many lights can go on one circuit breaker, you need to know what follows.
Before any circuit breakers can be installed, you must have an electrical panel. This box has the main electrical line coming in from outside. This line is then branched off to different circuit breakers.
There are many different types of circuit breakers. For a residence, there is one main circuit breaker that branches off into smaller amp (amperage) individual circuits. All the individual circuit breakers combined cannot exceed the total main amp. Each circuit breaker is designed to trip (shut off) when there is an excessive amount of power going through it.
Amperage, or current, is the amount of electrical energy flowing through any light fixture at any given time. The amount of amps will be clearly identified on the individual fixture.
Watts are a measure of the use of electrical power. One watt is equal to one volt multiplied by one amp.
Electrical wire carries electricity to the outlets or appliances from the circuit breaker. It is made of a metal that easily conducts electricity, usually copper, in an insulator. There are different wires made to allow certain loads.
To figure out "How Many Lights Can Be Installed on One Circuit Breaker," you have to know the following.
50 watt light equals less than 1/2 amp current flow at 120 volts.
You can put up to 30 lights (based on 50 watt light) on a 15 amp breaker.
You can put up to 40 lights (based on 50 watt light) on a 20 amp breaker.