RADT151 Homework #6 and All Quizzes MRO 5 (Electromagnetism)

A simple generator will produce which current type? A. AC B. DC

A. AC ( A simple generator design has the armature in continuous contact with the circuit and the nature of the rotation causes AC.)

Transformers operate best with: A. AC B. DC

A. AC (Because transformer operation is based on mutual induction they operate best with AC, which provides a "moving" magnetic field.)

A commutator ring in a generator design is attached to which of the following? A. Armature B. Magnet C. Brushes D. Circuit

A. Armature (The use of the commutator ring in the generator design is to attach it to the armature and allow the gaps of the commutator ring to temporarily break contact with the circuit.)

An iron bar exposed to a strong magnetic field may become which of the following? A. Artificial permanent B. Electromagnet C. Natural

A. Artificial permanent

What is the fundamental difference between conductors and insulators? A. Conductors have many free electrons. B. Insulators have many free electrons. C. Conductors have neutral atoms. D. Insulators have neutral atoms.

A. Conductors have many free electrons. (Johnston Pg. 33)

The flow of electrons in a conductor would be classified as: A. Electrodynamics B. Electrostatics C. Coulomb's law D. Electrification

A. Electrodynamics

If a magnetic material is placed in the field of a magnet, what happens to that field? A. It is distorted. B. It is not affected. C. It creates a space around the material. D. It is destroyed.

A. It is distorted. (Johnston Pg. 36)

Which scientist formulated a law that explains a principle of electromagnetic induction? A. Lenz B. Ohm C. Faraday D. Oersted

A. Lenz

If a circle with a dot in the center represents a wire carrying electric current toward you, which of the following is true? A. Magnetic flux lines flow counterclockwise. B. Magnetic flux lines flow clockwise.

A. Magnetic flux lines flow counterclockwise. (Using the right-hand rule and pointing your thumb towards you, you will see that the flux lines will flow counterclockwise.)

The induction motor operates based on what principle? A. Mutual induction B. Self-induction

A. Mutual induction (The induction motor utilizes a series of external magnets that induce a current and associated field in the rotor (central component) which is mutual induction.)

What is the coulomb as a unit of measure of electrical charges based on? A. Number of electrons B. Number of protons C. Temperature of conductor D. Direction of flow

A. Number of electrons (Johnston Pg. 32)

Which scientist used a compass and a wire carrying electric current to demonstrate and study electromagnetism? A. Oersted B. Lenz C. Ohm D. Faraday

A. Oersted (While all of these scientists should be familiar to you from your study of radiologic physics to this point, Oersted is the one credited for demonstrating electromagnetism.)

How are insulators incorporated into the use of electricity? A. They are used to contain electric flow. B. They increase electron flow. C. They add resistance to circuits. D. They increase temperature around electric flow.

A. They are used to contain electric flow. (Johnston Pg. 35)

What causes the armature to rotate in a simple motor? A. Two magnetic fields trying to align B. Heat production C. Mechanical force D. Armature does not turn in a motor.

A. Two magnetic fields trying to align (In a simple motor, a current is supplied to the armature and with this current is a magnetic field. This created magnetic field causes the armature to rotate as it tries to align with the external magnetic field.)

What happens to current as resistance increases? A. Increases B. Decreases C. Unaffected

B. Decreases

An iron bar wrapped with a wire carrying electric current is what class of magnet? A. Artificial permanent B. Electromagnet C. Natural magnet D. Nonmagnet

B. Electromagnet

Which type of magnet has many applications in electrical equipment? A. Artificial permanent B. Electromagnet C. Natural

B. Electromagnet

Converting mechanical energy to electrical energy is the purpose of which device? A. Transformer B. Generator C. Motor

B. Generator (The purpose of a generator is to convert mechanical energy to electrical energy through electromagnetic induction. )

When an uncharged metallic object experiences a shift of electrons in the electric field of another, this is electrification by: A. Contact B. Induction C. Friction

B. Induction (Johnston Pg. 33)

If a circle with an "X" in the center represents a wire carrying current away from you, which of the following is true? A. Magnetic flux lines flow counterclockwise. B. Magnetic flux lines flow clockwise.

B. Magnetic flux lines flow clockwise.

In which device does a commutator ring serve to feed current through an armature the same direction each time? A. Transformer B. Motor C. Generator

B. Motor ( In a simple motor the commutator ring serves to briefly break contact with the circuit so that current flows into the armature the same way each time.)

Which scientist conducted experiments demonstrating that a magnetic field created by a flow of electric current was greater than the Earth's magnetic field? A. Faraday B. Oersted C. Lenz D. Ohm

B. Oersted (Johnston Pg. 37)

Like poles of a magnet or charges of electric fields will: A. Attract B. Repel C. Behave differently depending on environment

B. Repel (Both electric and magnetic fields exhibit this property of attraction and repulsion. Like poles or charges repel, and unlike poles or charges attract.)

What is the unique electron characteristic of magnetic materials? A. They all occupy the same electron shell. B. They all orbit in predominately one direction. C. They all have positive charges. D. They all have the same number of electrons.

B. They all orbit in predominately one direction. (The orbital electrons of atoms of magnetic materials orbit in predominately one direction. It is this net spin that causes these atoms to be tiny magnets and overall give the material magnetic properties.)

According to the laws of magnetism, how many poles will an atomic magnet have? A. No poles at this level B. Two poles at this level C. One pole at this level D. Four poles at this level

B. Two poles at this level

The south poles of two magnets are placed 1 millimeter from each other. Which of the following describes the reaction? A. Very strong attraction B. Very strong repulsion C. No reaction will occur.

B. Very strong repulsion

The following describes four different coils. Which one, if moved through a magnetic field, would create the least voltage? A. 40 turns B. 30 turns C. 10 turns D. 20 turns

C. 10 turns (The lower the number of turns, the lower the induced voltage. This is a direct relationship; if you halve the turns, you halve the resultant voltage.)

If the number of coils of a conductor is 40 and the voltage is 110, what will the voltage be if the number of coils is increased to 80? A. 440 B. 55 C. 220 D. 880

C. 220 ( Increasing the number of coils increases the voltage. This is a direct relationship; if you double the number of coils, you double the voltage. )

Which of the following conductor angles, in relation to the magnetic field, will produce the greatest voltage? A. 20 degree angle to the field B. 45 degree angle to the field C. 90 degree angle to the field D. Parallel to the field

C. 90 degree angle to the field (The angular relation of the conductor to the field is another factor that determines the voltage induced. The greater the angle, up to 90 degrees -perpendicular - the greater the induced voltage because more coils will pass through the magnetic field per unit time.)

Platinum is magnetically classified as which of the following? A. Nonmagnetic B. Diamagnetic C. Paramagnetic D. Ferromagnetic

C. Paramagnetic (Platinum, gadolinium, and aluminum are common examples of paramagnetic materials which are weakly attracted to magnetic fields.)

What atomic characteristic of a magnetic material creates a dipole? A. They have no nucleus. B. They have no electrons. C. Their electrons spin in predominately one direction. D. They are positively charged.

C. Their electrons spin in predominately one direction. (Johnston Pg. 36)

At what distance would you expect two magnets to have the strongest reaction to each other? A. 1 yard B. 1 foot C. 1 inch D. 1/8 inch

D. 1/8 inch (According to the laws of magnetism, the force of attraction or repulsion of magnets follow the inverse square law. The smaller the distance, the greater the attraction.)

What aligns to form magnetic domains? A. Electrons B. Protons C. Neutrons D. Atoms

D. Atoms (Johnston Pg. 36)

Magnetic poles can exist separately from each other and may have only one pole. True or False?

False

Lines of magnetic flux traveling in the same direction will attract each other. True or False?

False (One of the characteristics of magnetic fields is that lines of flux in the same direction will repel each other. )

A magnet is formed when all of its "atomic magnets" align. True or False?

True

Heating a magnetized iron bar will cause it to lose some or all of its magnetism. True or False?

True

Tapping an iron bar against a solid object in a magnetic field will help magnetize that material. True or False?

True

The inverse square law applies to both electric and magnetic fields. True or False?

True

The relationship of electromagnetic radiation to distance (inverse square law) and the relationship between electromagnetic force and distance (Coulomb's law) are identical. True or False?

True

With electric fields, positive and negative charges exist separately. True or False?

True

Depending on the application of the right-hand rule, the thumb can indicate either current flow or direction of the magnetic field. True or False?

True (Although the original description of the right-hand rule uses the thumb to indicate the direction of current flow, a variation has the thumb indicating the direction of the magnetic field.)

The north and south ends of an electromagnet change each time an AC changes direction. True or False?

True (Because the magnetic field is created by and associated with the flow of current, each time the direction of current changes, the associated magnetic field changes.)

Rubbing a ferromagnetic material against a permanent magnet will magnetize that material. True or False?

True (Rubbing a ferromagnetic material against a permanent magnet will cause the domains of that material to align and magnetize that material. )