Please helpers! I wrote the first questions answer but from there i didnt know how to calculate.

What is special about a dc circuit ?

At 20∘c, the hole in an aluminum ring is 2.800 cm in diameter. you need to slip this ring over a steel shaft that has a room-temperature diameter of 2.804 cm . 1. to what common temperature should the ring and the shaft be heated so that the ring will just fit onto the shaft? coefficients of linear thermal expansion of steel and aluminum are 12×10−6 k−1 and23×10−6 k−1 respectively.

If an electric circuit is not grounded it is best to reach out and touch it to provide the ground a.true or b.false