How does the brightness of a bulb affected by addition of a cell in a circuit?

The brightness of a bulb in a circuit is affected by the voltage supplied to it. When a cell is added to a circuit, it increases the voltage supplied to the bulb, which in turn increases the brightness of the bulb. This is because the voltage is directly proportional to the brightness of the bulb - the higher the voltage, the brighter the bulb will be.

The brightness of a bulb is directly proportional to the amount of current flowing through it. When a cell is added to a circuit, the total voltage in the circuit increases, which causes more current to flow. This increased current results in a brighter bulb.

The relationship between voltage, current, and resistance is given by Ohm's law:

```
V = IR
```

where:

- V is the voltage in volts
- I is the current in amps
- R is the resistance in ohms

When the voltage in a circuit increases, the current also increases, assuming the resistance remains constant. This is because the increased voltage provides more energy to push the electrons through the circuit.

The brightness of a bulb is also affected by the resistance of the bulb. A bulb with a higher resistance will draw less current than a bulb with a lower resistance. This is because the higher resistance makes it more difficult for the electrons to flow through the bulb.

Therefore, the brightness of a bulb is determined by both the voltage in the circuit and the resistance of the bulb. Adding a cell to a circuit will increase the voltage, which will cause the bulb to draw more current and become brighter.