# Physics HELP

Evelyn wears glasses whose wire frames are shaped like to circles, each with an area of 2.0x10^-3 m^2. The horizontal component of the earths' magnetic field in Evelyn's hometown is 1.9x10^-5 T. If Evelyn turns her head back and forth, rotating it through 90degrees every 0.5s, what is the induced voltage in the wire frame of one eyepiece.

1. Induced emf = - (Rate of change of magnetic flux)
= - (Change in magnetic flux)/(Change in Time)
= - d(Ф)/dt
= - (Final magnetic flux - Initial Magnetic Flux)/0.5
= - (B*A*cos(θ2) - B*A*cos(θ1))/0.5
= - B*A( cos(θ2) - cos(θ1) )/0.5

Your question gives you the value of B, of A, and gives you the difference between the two angles as 90 degrees. Plug in the values, and solve.

(The negative sign may be considered at the end since it only describes the direction of the induced emf)

posted by Arora

## Similar Questions

1. ### physics

Evelyn wears glasses whose wire frames are shaped like to circles, each with an area of 7.0x10^-4 m^2. The horizontal component of the earths' magnetic field in Evelyn's hometown is 4.9x10^-5 T. If Evelyn turns her head back and
2. ### Physics

Evelyn wears glasses whose wire frames are shaped like to circles, each with an area of 8.0x10^-4 m^2. The horizontal component of the earths' magnetic field in Evelyn's hometown is 3.9x10^-5 T. If Evelyn turns her head back and
3. ### Math

In a company, the men who do not wear glasses are thrice as many as the men who do, while the women who do not wear glasses are ten more than the women who do. The probability that an employee wears glasses is 3/10. If selected
4. ### Math

Evelyn drinks 8 glasses of water a day,which is 56 glasses of water a week. How many glasses of water does she drink in a year?(1 year =52 weeks )
5. ### Math

Three picture frames are on a dresser.two are shaped like squares and the other is a trapazoid. how many sides are there in the frames altogether? Please help today
6. ### Maths

20 pupils,8 males, 3 males wear glasses whats the probability that the first student is mals and wears glasses?
7. ### math

Suppose that the population of a certain townis made up of 45% of men and 55% of women. Of the men, 40% wear glasses, abd of the women, 20% wear glasses. Given that a person chosen at random from the town wears glasses, what is
8. ### geometry

A wire 10 meters ong is to be cut into two pieces. One piece wil be shaped as a square, and the other piece will be shaped as a circle. (piece one is 4x, piece two is 10-4x) a)Express the total area A enclosed by the pieces of
9. ### HELP-PROBLEM SOLVING IN MATHEMATICS

a piece of wire of length 136(pai) is cut to form 8 circles. the radius of the circles differ from each other, in sequence, by 1 cm. a) find the radius,r b) find the number of complete circles that can be formed if the original
10. ### Statistics

A recent survey found that 70% of all adults over 50 wear glasses for driving. You randomly select 30 adults over 50, and ask if he or she wears glasses. Decide whether you can use the normal distribution to approximate the

More Similar Questions