Voltage drops - i don't understand

  • Thread starter Thread starter debwaldy
  • Start date Start date
  • Tags Tags
    Voltage
AI Thread Summary
The discussion centers on calculating the necessary voltage drop across a capacitor in a circuit with a 750W, 100V lamp connected to a 230V supply. The user is confused about determining the current and voltage drop, initially calculating current as I = 750W/100V. A participant clarifies that the voltage drop required across the capacitor is 130V, derived from the difference between the supply voltage and the lamp's voltage. To find the capacitance, they suggest using a capacitor equation that incorporates frequency. Understanding these calculations is essential for completing the problem.
debwaldy
Messages
34
Reaction score
0

Homework Statement


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 don't 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.


Homework Equations


P = IV
V=IX X = capacitive reactance



The Attempt at a Solution


I think the current is given by
I = 750W/100V?
I don't know how to calculate the voltage drop.Thanks for any help and tips
Debs:smile:
 
Physics news on Phys.org
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).
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »

Thread 'Rolling without slipping on a curved surface'

Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
View full post »

Similar threads

Phase shift between voltage and current
Replies
3
Views
1K
Understanding Voltage Drop in a Circuit
Replies
10
Views
1K
The voltage across an AC source and a resistance in series
Replies
4
Views
2K
Understanding example in Wikipedia entry for open circuit voltage
Replies
3
Views
2K
Figuring out how to approach capacitor problem
Replies
9
Views
2K
AC voltage across a parallel branch
Replies
5
Views
2K
Change in Capacitor for largest possible Current
Replies
2
Views
2K
What Current Flows in a Coil at 230V, 50Hz?
Replies
5
Views
2K
Why don't voltages add up numerically in an LCR AC circuit?
Replies
5
Views
3K
Confused about voltage & current -- Please check my understanding
Replies
2
Views
2K

Hot Threads

Recent Insights

Back
Top