Magnetic flux against e.m.f (V)

[Googl]

Hi,

Could someone confirm for me please. As the magnetic flux increases does the e.m.f increase as well? (solenoid) And if we were to plot a graph of the two against each other, the graph will have a positive line/curve. My graph has a negative curve suggesting that as flux increases e.m.f decreases, that's wrong right?

Thanks.

 

[marcusl]

It depends on how you defined the positive and negative terminals of your solenoid relative to the field inside. Here's how to figure it out.

A changing magnetic flux $$\phi$$ produces a "back emf" $$\varepsilon$$ according to

$$\varepsilon=-\frac{d\phi}{dt}$$

According to Lenz's Law, the sign of the emf is such as to produce a current that produces a flux that opposes the external change in flux.