A flat coil of wire has an area A, N turns, and a resistance R. It is situated in a magnetic field, such that the normal to the coil is parallel to the magnetic field. The coil is then rotated through an angle of 90˚, so that the normal becomes perpendicular to the magnetic field. The coil has an area of 1.5 × 10-3 m2, 50 turns, and a resistance of 110 Ω. During the time while it is rotating, a charge of 9.5 × 10-5 C flows in the coil. What is the magnitude of the magnetic field? B =

Johnny created an electromagnet out of a solenoid (a coil of wires with 20 loops), an iron core (of 1 nail), and a single 9 V battery. When Johnny does this, he creates a small magnetic field that allows him to pick up 2 paper clips. Using a CER format, explain to Johnny three things he could change that would increase the strength of his magnetic field and why each change increases the magnetic field. You may want to write three paragraphs to make this easier for the reader to understand

it is very well related to a lot of things but with my limited knowledge i can confidently say that the answer is space.

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.