An experiment is conducted on a long straight wire of diameter d. a constant current is sent through the wire and the magnetic field on the surface of the wire is measured to be b1. the experiment is then repeated with the same current but with a wire of diameter 2d. the magnetic field measured on the surface of this second wire will be which of the following?

b1, b1 / 4, 4b1, b1 / 2

As part of your daily workout, you lie on your back and push with your feet against a platform attached to two stiff springs arranged side by side so that they are parallel to each other. when you push the platform, you compress the springs. you do an amount of work of 79.0 j when you compress the springs a distance of 0.230 m from their uncompressed length. (a) what magnitude of force must you apply to hold the platform in this position? (b)how much additional work must you do to move the platform a distance 0.230 m farther? (c) what maximum force must you apply to move the platform a distance 0.230 m farther?