# Homework Help: Voltage fall

1. Feb 20, 2008

### ritwik06

1. The problem statement, all variables and given/known data

A refrigerator is marked 80W and 250 V. What is likely to happen if the voltage falls to
50V?

2. Relevant equations

P=V^2/R
V=IR

3. The attempt at a solution
---------------------------------------------------------
R=V^2/P
=250*250/80
=781.25 ohm
Assuming the resistance to be constant.
--------------------------------------------------------
Current earlier=P/V
=80/250
=0.32 A
----------------------------------------------------

Current when voltage falls to 50V

=50/781.25 (V=IR)
=0.064 A

---------------------------------------------------

Power will also decrease.
P=VI
=50*0.064
=3.2 W

******************************************

It seems that the appliance will be damaged. I have no idea about anything further. Am I right? I have written everything i could make out. Please help me now.

2. Feb 20, 2008

### chroot

Staff Emeritus
Your reasoning looks entirely correct to me. Of course, in the real world, you're probably right -- the appliance may well be damaged if its compressor can't turn and it just sits there soaking up stall current until it overheats.

- Warren