Voltage drops - i don't understand!

1. Dec 5, 2007

debwaldy

1. The problem statement, all variables and given/known data
Hi, this question is really confusing me and preventing me from completing the rest of the question. It is probably a very simple problem but i just dont understand so any help would be much appreciated.

A metal- filament lamp,rated at 750W, 100V, is to be connected in series with a capacitor across a 230V, 50Hz supply. Calculate the voltage drop across the capacitance required, the current, the capacitance, phase angle between the supply voltage and current.

2. Relevant equations
P = IV
V=IX X = capacitive reactance

3. The attempt at a solution
I think the current is given by
I = 750W/100V?
I dont know how to calculate the voltage drop.Thanks for any help and tips
Debs

2. Dec 5, 2007

marcusl

The voltage drop needed across the capacitor to keep the bulb happy is 230 - 100 = 130V. To find the capacitance, look for a capacitor equation relating the voltage to the rate of change of the current (it will involve the frequency).