A 2.5 W wire is curled into an elliptical loop with an area of 1.2 m^2 and is placed horizontally QUESTION CONTINUED IN DESCRIPTION

Question

A 2.5 W wire is curled into an elliptical loop with an area of 1.2 m^2 and is placed horizontally on a table where it is embedded in a 30 mT magnetic field that points upward. The ends of the ellipse are then pulled, stretching it out and reducing the area to 0.1 m^2. As the ellipse narrows, a current of 3.6 mA is generated in the wire. How long does it take to change the ellipse’s shape?

Answer 1

Hello Ashley

This is a question on Electromagnetic induction( based on Faraday's Laws )

and Power= Voltage* Current ( Formula)

According to Faraday's laws

The induced EMF ( Volts) is given by

E = - (Rate of change of magnetic flux) -ve sign only signifies only direction of induced EMF

= Change in flux / Time

Change in Flux in this case = Magnetic field* Change in area=30*10^-3 * (1.2-0.1) =3.3*10^-2 Weber

So induced EMF = 3.3*10^-2 /time...... Eq 1

So time = 3.3*10^-2 /EMF

But Power = Voltage *Current = EMF* Current = 2.5 W , But Current =3.6*10^-3 Amp

EMF*3.6*10^-3 =2.5

Now plug in EMF from Eq 1 and get time to change the shape of elipse