Question

1. ____ wrote the book on the lodestone and magnetic bodies, and on the great magnet the earth (de magnete).

charles de coulomb
pierre le pèlerin de maricourt
william gilbert
sir isaac newton

1. imaginary lines that indicate the direction and strength of a magnets magnetic field are called ____.

declination lines
isogonic lines
lines of flux
isoclinic lines

1. which of the following statements regarding permeability is not true?

a highly permeable substance will increase the force of attraction when placed between two magnets.
aluminum is a highly permeable substance.
a highly permeable substance can act as a magnetic shield.
the higher the permeability of a substance, the more easily it is magnetized.

1. magnetic resonance imaging produces three - dimensional images by detecting the ____ of a patients atoms when exposed to a powerful magnet.

electron spin
proton pairs
nucleus spin
number of neutrons

1. which of the following statements regarding domain theory is not true?

an object will have a magnetic field when most of its domains are lined up in the same direction.
a domain is a group of aligned atoms having a single magnetic field.
domains can be physically knocked out of alignment by striking the magnet.
a typical domain is about one centimeter across.

1. a permanent magnet will lose its magnetism when heated to its ____ point.

curie
coercivity
oersted
agonic

1. an electromagnet with twenty loops of wire has a strength of 100 n. how many loops of wire are needed for the strength to be 400 n?

10
40
80
100

1. the angle that a compass needle deviates from true north is called the angle of ____.

declination
deviation
deflection
induction

1. the angle of inclination (also called magnetic dip) is 0° at the ____.

north magnetic pole
south magnetic pole
agonic line
magnetic equator

1. the doughnut - shaped belts of high - speed charged particles that help protect the earth from the solar wind are called the ____.

auroras
magnetosphere
van allen radiation belts
coulomb radiation belts

Explanation:

Step1: Determine the relationship

The strength of an electromagnet is directly proportional to the number of loops of wire. Let \(n_1 = 20\) loops, \(F_1=100\ N\), \(F_2 = 400\ N\), and \(n_2\) be the unknown number of loops. The proportion is \(\frac{n_1}{F_1}=\frac{n_2}{F_2}\).

Step2: Solve for \(n_2\)

Cross - multiply the proportion: \(n_2=\frac{n_1\times F_2}{F_1}\). Substitute \(n_1 = 20\), \(F_1 = 100\), and \(F_2=400\) into the formula: \(n_2=\frac{20\times400}{100}\). First, calculate \(20\times400 = 8000\), then \(8000\div100=80\).

Answer:

80