# A2 experiment and I'm totally confused

S

#### sexysam_short

Hello!

I've recently done an A2 experiment and I'm totally confused as to how to interpret the results! I would be really greatful for some help!

I basically droped a magnet through a coil and measured the voltage with a data logger and what not! I get that there's an induced voltage, because it's a magnet being dropped through a coil, but the graph looks like a sine wave at the point when the magnet is passing through the coil. Why does it?

Thanks lots,

Sam

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#### Sirus

Why is a voltage induced when the magnet passes through the coil? Current is induced in the coil in response to what...?

#### aekanshchumber

As you might know that the described phenomena was discovered by M. faraday.
When a bar magnet is droped in coil the magnetic feild lines, associated with the magnet, linkage with the coil change. It cause change in magnetic field changing magnetic field force electron in the coil to move, as the force is same on all eceltrons and in same direction they start flowing and the current is induced.
As the force on electrons is dependent on sinx (x is angle of allingment) the induced current hence voltage are sin functions.

S

#### sexysam_short

Thanks for the help! But, I get why it would be the positive part of the sine wave, because of the induced currect, but why does the graph go negative?

#### ylem

Me again (changed my username because I thought this word was fantastic! lol)

I've just realised I actually don't know how you get an induced current? Could someone please explain it to me?!

Thanks lots!

#### TillEulenspiegel

You get the positive sine as more of the magnet is centered in the coil ending when the magnet is centered and the coil is saturated ( to the extent of the available magnetic field from the magnet)..conversly when the magnet exits the v approaches 0 . The coil has a stored magnetic field and when that field collapses the expressed V is 180 degrees out of phase with the V induced by the magnet. Thats why we use a protection diode on a relay coil reversed biased and why use a ballast resistor on a car coil.

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