# physics EM

Shrinking Loop. A circular loop of flexible iron wire has an initial circumference of 167 cm, but its circumference is decreasing at a constant rate of 10.0 cm/s due to a tangential pull on the wire. The loop is in a constant uniform magnetic field of magnitude 0.600 T, which is oriented perpendicular to the plane of the loop.

Find the (magnitude of the) emf EMF induced in the loop after exactly time 1.00 s has passed since the circumference of the loop started to decrease.
im pretty sure ive been doing it right but as usual probaly a mistake.

1. 👍
2. 👎
3. 👁
1. Area A is related to circumference C by

A = pi r^2 = pi * [C/(2 pi)]^2
= [1/(4 pi)]C^2

C = 1.67 - 0.1 t (in meters)
dA/dt = [1/(2 pi)] C dC/dt
= -(0.05/pi) C

V(t) = B*dA/dt = B (0.05/pi) C(t)
With B in Tesla, the answer will be in volts. Choose t = 1 second to get C. I have thrown out the minus sign, since we don't care about polarity

Check my math and thoughts. No guarantees here.

1. 👍
2. 👎
2. it all looks right and what i did also. yet it seems like the answer should be larger because whenever i input it into the program it seems like its too small because it says the flux should occur since the area is changing. It seems to be taking it as zero. we converted it to meters so it should be ok.

1. 👍
2. 👎
3. nvm dangit it works. just off by a small amount.

1. 👍
2. 👎
4. Spencer is wrong. Just so you guys know

1. 👍
2. 👎
5. @drwls math mustve been different in 2008 because i have no idea what you did

1. 👍
2. 👎

## Similar Questions

1. ### Physics-Please check

Electricity may be generated by rotating a loop of wire between the poles of a magnet. The induced current is greates when: a.Plane of loop makes an angle 45 degrees with the magnetic field b.The plane of the loop is parallel to

2. ### physics

The drawing shows a version of the loop-the-loop trick for a small car. If the car is given an initial speed of 4.6 m/s, what is the largest value that the radius r can have if the car is to remain in contact with the circular

3. ### PHYSICSI

The rotating loop in an AC generator is a square 11.0 cm on a side. It is rotated at 60.0 Hz in a uniform field of 0.800 T. Calculate the following quantities as functions of time t, where t is in seconds. (a) the flux through the

4. ### PHYSICS

A 14 cm diameter circular loop of wire is placed in a 0.58 T magnetic field. (a) When the plane of the loop is perpendicular to the field lines, what is the magnetic flux through the loop? (b) The plane of the loop is rotated

1. ### Physics

A pilot, whose mass is 91.0 kg, makes a loop-the-loop in a fast jet. Assume that the jet maintains a constant speed of 125 m/s and that the radius of the loop-the-loop is 0.478 km. What is the apparent weight that the pilot feels

2. ### Physics

A single conducting loop of wire has an area of 7.4 10-4 m2 and a resistance of 110 Ω. Perpendicular to the plane of the loop is a magnetic field of strength 0.18 T. At what rate (in T/s) must this field change if the induced

3. ### physics

A mass m = 76.0 kg slides on a frictionless track that has a drop, followed by a loop-the-loop with radius R = 19.7 m and finally a flat straight section at the same height as the center of the loop (19.7 m off the ground). Since

4. ### Physics

A 20-cm-diameter circular loop of wire is placed in a 0.57-T magnetic field. Part A When the plane of the loop is perpendicular to the field lines, what is the magnetic flux through the loop? Part B The plane of the loop is

1. ### physics

A long, vertical, straight wire carries a current I going upwards. The wire is perpendicular to the plane of a circular metal loop and passes through the center of the loop. The loop is allowed to fall and maintains its

2. ### Physics

A 2.00 cm x 2.00 cm square loop of wire with resistance 1.30×10^−2 Ohms is parallel to a long straight wire. The near edge of the loop is 1.00 cm from the wire. The current in the wire is increasing at the rate of 110 A/s. What

3. ### physics

A mass m = 88 kg slides on a frictionless track that has a drop, followed by a loop-the-loop with radius R = 15.5 m and finally a flat straight section at the same height as the center of the loop (15.5 m off the ground). Since

4. ### Physics

An infinite straight wire carrying a current I=5 A flowing to the right is placed above a rectangular loop of wire with width w=11 cm and length L=27 cm, as shown in the figure below. The distance from the infinite wire to the