# What resistance is needed if current is .300 A?

pebbles

## Homework Statement

A 75.0 W bulb is connected to a 120 V source. A lamp dimmer puts a resistance in series with the bulb. What resistance would be needed to reduce the current to .300 A?

R=V/I

## The Attempt at a Solution

R=120/.3A=400 ohms. The answer is 210 ohms. What am I missing?

## Answers and Replies

Phrak
Here's another relevant equation.

$$(R_{bulb} + R_{dimmer} = V_{total}/I$$

montoyas7940
Here is one more:

$$P=V^2/R$$