- #1
DarkStalker
- 28
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First of all I'd like to say hello. Secondly, my Physics is not very exceptional, so please don't mock me if I ask sth very dumb. :)
A power station giving an output power of 100kW at 20000V is connected by cables to a factory.
If the resistance of the cables is 5.0 Ω, calculate:
(a) the current flowing in the cables,
P=VI
I tried solving this using "V=IR". Here's my attempt.
V=IR
20000 = I x 5
I = 20000/5 = 4000 A.
The actual solution given is:
Since P (Output) = IV where I is the current in the cables
I=P/V
= 100kW/20000
=...= 5A
I just need to know why we can't use "V=IR". My guess is it has to sth about a.c. or d.c.
Homework Statement
A power station giving an output power of 100kW at 20000V is connected by cables to a factory.
If the resistance of the cables is 5.0 Ω, calculate:
(a) the current flowing in the cables,
Homework Equations
P=VI
The Attempt at a Solution
I tried solving this using "V=IR". Here's my attempt.
V=IR
20000 = I x 5
I = 20000/5 = 4000 A.
The actual solution given is:
Since P (Output) = IV where I is the current in the cables
I=P/V
= 100kW/20000
=...= 5A
I just need to know why we can't use "V=IR". My guess is it has to sth about a.c. or d.c.