# How many bulbs should be connected in series in a Christmas tree garland if the garland

**How many bulbs should be connected in series in a Christmas tree garland if the garland is designed to be connected to a network with a voltage of U = 220 V? Each light bulb says: power P = 2 W, current I = 0.3 A.**

U = 220 V.

P1 = 2 W.

I1 = 0.3 A.

n -?

For a series connection of conductors, the formulas are valid: U = U1 + U2 + U3, I = I1 = I2 = I3, R = R1 + R2 + R3.

For n identical bulbs U = n * U1.

The power of one light bulb is P1 = 2 W.

The power of a light bulb is determined by the formula: P1 = U1 * I1, where U1 is the voltage in one light bulb, I1 is the current in the light bulb.

Let’s find the voltage in one light bulb: U1 = P1 / I1.

U = n * P1 / I1.

Let’s express the number of bulbs n in a garland: n = U * I1 / P1.

n = 220 V * 0.3 A / 2 W = 33.

Answer: there are n = 33 light bulbs in the garland.