# How much currect flows through wall outlet?

Discussion in 'General Electronics Chat' started by sensor, Sep 29, 2012.

1. ### sensor Thread Starter Member

Sep 8, 2009
19
0
I think, it's 220V AC from wall outlet.

So how much current flows to bulb and fan from wall outlet?

V = RI, P=VI

What is the value of R (ohm) ? What is the value of P (power=Joul) ?

2. ### sbixby Active Member

May 8, 2010
57
10
P=VI...

For a 100W lightbulb --

100W = 220V * I

I = 100W/220V = 0.4545... A

This is purely by the numbers, since a lightbulb's actual power usage will vary.

3. ### sensor Thread Starter Member

Sep 8, 2009
19
0
Where did you get the value of P (power) ?

4. ### vpoko Active Member

Jan 5, 2012
267
51
It's on the light bulb. If you get a light bulb labeled 100W, it should use approximately 100W.

More broadly, the amount of current that flows through an outlet is determined by the load. In this case it's 100W, but that depends on what's plugged in.

5. ### sensor Thread Starter Member

Sep 8, 2009
19
0
What do you mean by load?

It's a bulb with 18W.

6. ### vpoko Active Member

Jan 5, 2012
267
51
Load is the cumulative resistance of the entire circuit (not the sum of all resistors, but using the proper formulas for serial and parallel parts of the circuit). In a light bulb, it's already labeled for you. Since you know it's an 18W bulb, and you know the outlet is 220V, just plug those into your formula P=VI. 18=220*I. Now, to solve for I, divide both sides by 220. I=18/220=0.0818A.

7. ### Wendy Moderator

Mar 24, 2008
21,413
2,946
The equation is simple.

P = V x I

18W = 220VAC x I

The rest is algebra.

BTW, light bulbs and many other appliances are measured in watts, not joules.