Purchase a heater with a high resistance because P= I^2 R

[heartOFphysic]

A student goes out to purchase an electric heater for his flat. The salesman says that, to
get more heat, he should purchase a heater with a high resistance because P= I^2 R
but the student thinks that a low resistance would be best, because P= V^2/R

explain who is correct?

Hmmm I'm rather stumped on this one, any pointers/ tips to head me off in the right direction?

Thanks

 

[MartinCarr]

Yes, but looking at those two equations what can you change at home? Voltage or current? In practice all you can change is the current flow

 

[gneill]

Consider the power supply in the flat. What are its characteristics?

 

[heartOFphysic]

The current is alternating in a house supply, I guess?

 

[gneill]

The current is alternating in a house supply, I guess?

While that is certainly true, what other specifications does it have?

 

[heartOFphysic]

A current causes a heating effect!

 

[MartinCarr]

In your house you can only change the current. Think of it a different way, something with a high resistance reduces current flow, but gets hot in the process

 

[Pengwuino]

A current causes a heating effect!

Sure, but what can you change at the flat? The power that you receive when you plug into an outlet is fixed at 120V/240V/whatever, depending on the country you live in. You can't change that.

P = I^2 R is dependent on the current and the resistance. P = V^2/R is dependent only on the voltage. Since the voltage is fixed, the 2nd equation tells you everything you need to know to answer your question. The problem with the first equation is that the current is not fixed and when you change the resistance, the current will change as well, so you can't immediately know "what happens when I change R".